Each year, a new group of rookies sets out to make a mark in the Major Leagues, and in 2018, many of these young players have made history with their performances. They're fueling clubs during postseason races, as well as giving fans a glimpse of what's to come in the years ahead.
With the aid of all 30 MLB.com beat writers, here's a look at each team's best rookie this season:
Video: Callis looks at rookies' long-term futures
AMERICAN LEAGUE EAST
Blue Jays: Ryan Borucki
Borucki has opened his Major League career with quality starts in 10 of his first 15 outings. Even though Borucki did not make his debut until the end of June, he has the third-most starts of at least six innings and two runs or fewer among Major League rookies. Only San Francisco's Dereck Rodriguez has registered more of those starts this season. Borucki appears to be a future cornerstone of the Blue Jays' rotation and his rookie campaign has been an overwhelming success with a 3.86 ERA.
Orioles: Cedric Mullins
It's been a tough year for Baltimore, but Mullins has given O's fans a glimmer of hope in the past two months. Since becoming the first Oriole to record three hits in his debut, the center fielder -- who moved Adam Jones over to right -- has showcased his range and speed and has become a table-setter for a lineup that sorely needs more dynamic players.
Rays: Joey Wendle
Tampa Bay acquired Wendle from Oakland during the Winter Meetings -- the same day the Yankees finalized their acquisition of Giancarlo Stanton. Many found humor in how the Rays "answered" their division foe's acquisition. Wendle has hardly been a joke, though. He's played second base, third base, shortstop, right field and left field. While Wendle's glove has been dazzling as billed, particularly at second, his bat has been equally so. He always seems to be in the middle of rallies. Wendle has above-average speed and runs out every ball, and he's shown decent power. He has been a big reason for Tampa Bay's marked improvement this season.
Red Sox: Brian Johnson
Out of options, Johnson had no option but to become a dependable contributor for the Red Sox this season, and that's exactly what he has done. Though he has unspectacular numbers (4-4, 4.24 ERA), Johnson has been one of the most important members of the pitching staff for manager Alex Cora because of his ability to move seamlessly between the bullpen and starting rotation, and often doing both roles within days of each other. In 12 starts, Johnson is 4-2 with a 4.06 ERA. He could have a few more wins, but he was taken out just shy of five innings numerous times.
Yankees: Miguel Andujar
Nothing was handed to Andujar, who made the most of an early-season opportunity when Brandon Drury landed on the disabled list to grab hold of the third-base job. Andujar's calling card is his bat, and he quickly cemented a reputation as an extra-base hit machine, tallying the third-most extra-base hits by a rookie in Yankees history behind Joe DiMaggio (88) and Aaron Judge (79). The AL Rookie of the Month in June and August, Andujar has worked to polish his defense. With Gleyber Torres also enjoying a strong season, the Yanks have two legitimate choices to follow Judge as the AL Rookie of the Year Award winner.
Video: BOS@NYY: Andujar opens scoring with a solo HR in 2nd
Indians: Shane Bieber
Indians manager Terry Francona jokes that Chris Antonetti, the team's president of baseball operations, did not bring Bieber to MLB camp in the spring because the manager would not have let the pitcher return to the Minors. Bieber, 23, cruised through Double-A and Triple-A, posting a 1.47 ERA with 77 strikeouts vs. seven walks in 79 2/3 innings. When the back of Cleveland's rotation ran into some issues, Bieber rose to the big leagues. He debuted in late May and returned for good in June. The rookie has enjoyed a promising campaign and figures to be a part of the Tribe's postseason pitching staff.
Royals: Brad Keller
Keller, a right-hander, was an absolute steal in the Rule 5 Draft. He started the season in the bullpen and eventually graduated to the rotation, where he has been arguably the Royals' best starter and certainly a top-of-the-rotation guy moving forward. Opposing hitters throughout the season have called facing Keller an "uncomfortable at-bat." His four-seam fastball, which hovers around 93-95 mph, moves like a cutter, and he has worked to develop an effective slider and changeup. During a recent six-game stretch, Keller went 4-1 with a 1.85 ERA, permitting just a .645 OPS. While Keller, 23, likely won't win the AL Rookie of the Year Award -- especially with Shohei Ohtani, Torres and Andujar in the running -- he at least deserves some consideration. Keller is a lock for the rotation in 2019.
Tigers: Niko Goodrum
The Tigers took a chance on the former Twins second-round pick, extending a Spring Training invite in the hopes that his versatility and athleticism would help him stick while learning on the job in the big leagues. Much to their surprise, Goodrum has become essentially an everyday player and a cog in Detroit's lineup, with a .741 OPS that ranks second on the team to Nicholas Castellanos. He has made a start at every defensive position except center field, catcher and pitcher.
Twins: Jake Cave
The Twins took a chance on Cave in March, acquiring him from the Yankees for Minor League right-hander Luis Gil, and Cave has responded with a strong rookie season. The 25-year-old wasn't expected to play much this season, but with center fielder Byron Buxton out most of the year because of injuries and offensive inconsistency, the left-handed-hitting Cave has filled in nicely. He's capable of playing all three outfield positions and has shown some power offensively, hitting .257/.300/.458 with 11 homers and 13 doubles through his first 82 career games.
White Sox: Daniel Palka
The White Sox picked up the left-handed slugger off waivers from the Twins on Nov. 3, 2017. While he didn't break camp with the team, Palka not only leads the White Sox in home runs, but also set a single-season franchise record for most homers from a left-handed-hitting rookie. Palka has a knack for the big hit, having knocked out six home runs in the ninth inning. Left-handed reliever Jace Fry made a solid late-inning rookie impression, but Palka provided the biggest power boost.
Video: CWS@CLE: Palka breaks scoreless tie with HR to center
Angels: Shohei Ohtani
A rocky Spring Training created some questions about how Ohtani's talent would translate to the Majors, but he quickly erased those doubts once the regular season began. For two months, he dazzled as a two-way phenom for the Angels, emerging as a dominant right-handed pitcher with a triple-digit fastball and devastating splitter and an impact left-handed bat with impressive raw power. An elbow injury derailed his magical season and led to a Tommy John surgery recommendation earlier this month, but it hasn't prevented Ohtani from continuing to hit. He is the first player to log 10 pitching appearances and hit 20 home runs in a season since Babe Ruth in 1919, making him a front-runner for the AL Rookie of the Year Award.
Video: SEA@LAA: Ohtani goes back-to-back with Trout for 20th
Astros: Max Stassi
Stassi made his Major League debut during the Astros' 111-loss season of 2013, and he has bounced between the big leagues and Triple-A each season since while maintaining his rookie status. He's spent most of this year as Houston's backup catcher to Brian McCann, and he is hitting .233 with eight homers and 27 RBIs through 85 games. Stassi was on pace to catch more games than McCann, who missed a chunk of time with knee surgery, and Martin Maldonado, who was acquired in a July trade and cost Stassi significant playing time down the stretch.
Athletics: Lou Trivino
Trivino has been an absolute godsend for what's become a deep and dangerous Oakland bullpen, arriving in late April and quickly taking over setup duties behind All-Star closer Blake Treinen with a high-90s fastball and a mid-90s cutter -- a devastating duo. The flamethrowing right-hander singlehandedly bridged the gap for much of the first half before the midseason arrivals of Jeurys Familia, Shawn Kelley and Fernando Rodney, working multiple innings more times than not. Center fielder Ramon Laureano, who has been superb on both sides of the ball since his August promotion, also deserves consideration.
Mariners: Daniel Vogelbach
The 25-year-old first baseman made the Opening Day roster after a huge spring, then was sent down when he struggled at the plate in April. But after putting up good numbers again in Triple-A, Vogelbach has flashed his power potential with a couple of big home runs this week as a September callup, including a game-winning pinch-hit grand slam to beat the Astros on Monday.
Rangers: Ronald Guzman
This is a tossup between Guzman and Isiah Kiner-Falefa, who did a terrific job in a utility role that included time at catcher. But Guzman has emerged as the Rangers' first baseman of the future by showing power, run production and superb defensive ability. There is still more improvement and development needed, but Guzman is among the AL rookie leaders in home runs and RBIs. His emergence also allowed Joey Gallo to take over in left field, which had been a troubled spot for Texas.
NATIONAL LEAGUE EAST
Video: STL@ATL: Acuna Jr. belts a solo smash for his 26th HR
Braves: Ronald Acuna Jr.
Acuna has lived up to his top prospect status, as he spent the season's second half producing numbers baseball has seldom seen from a player who has not yet turned 21 years old. He introduced himself to the Majors in April and then suffered a late-May knee injury that sidelined him for a month. But when Acuna was moved to the top of Atlanta's lineup immediately after the All-Star break, the 20-year-old outfielder suddenly became one of the game's top catalysts and power threats. He became a strong NL Rookie of the Year Award candidate and likely earned some down-ballot NL MVP Award consideration.
Marlins: Brian Anderson
Not only has Anderson been the Marlins' top rookie in 2018, he has established himself as one of the young faces of the franchise. He's also built a case to be a top-five finisher in the NL Rookie of the Year Award balloting. On the big league roster from wire to wire, Anderson has played third base and right field. He will lead all NL rookies in games played and hits.
Mets: Jeff McNeil
McNeil was never a top prospect, and when he arrived in the big leagues, he first drew attention for his unusual knobless bat. But since he took over at second base following the Asdrubal Cabrera trade, he's been a revelation at the plate, commanding attention for his outstanding contact ability and all-around hitting prowess. McNeil hasn't slowed down, either -- he leads all rookies in hitting since his July 24 debut, including 17 multihit games in 54 contests, and is second among all players in triples in that span, with five.
Nationals: Juan Soto
Soto wasn't even the Nats' most heralded prospect coming into the year -- that was Victor Robles. But he's hit at an almost unprecedented level for his age, putting himself on lists alongside names like Griffey and Harper. Soto's combination of plate discipline and power marks him as a future star. He's not only a top NL Rookie of the Year Award candidate; he might even get some down-ballot consideration in the crowded NL MVP Award field.
Video: Must C Classic: Soto youngest to swipe 3 bags in game
Phillies: Seranthony Dominguez
One of the reasons the Phillies held first place in the NL East as late as Aug. 12 is Dominguez, who joined Philadelphia's bullpen in May. He posted a 1.85 ERA in 34 appearances through Aug. 3, striking out 49 and walking 13 in 39 innings, becoming manager Gabe Kapler's most trusted weapon with the game on the line. Dominguez struggled down the stretch as the former starter adjusted to a new role, but there is no question NL East batters are not looking forward to facing him in the future.
Brewers: Freddy Peralta
Taylor Williams pitched in more games and Corbin Burnes is playing the most significant role among Brewers rookies down the stretch, but in terms of aggregate value this season, Peralta gets the nod. By making 14 starts, including a history-making 13-strikeout Major League debut on Mother's Day, Peralta helped hold together a starting rotation that was a quiet strength for much of the year despite Jimmy Nelson's year-long absence and significant disabled list time for Zach Davies, Wade Miley and others. Among Major League starters who pitched at least 70 innings, only Chris Sale had a lower opponents' average than Peralta.
Cardinals: Jack Flaherty
With respect to Harrison Bader (3.5 fWAR), Jordan Hicks (105 mph fastball) and Yairo Munoz (.275 average), it's Flaherty who has emerged as the star of St. Louis' loaded rookie crop -- and the Cardinals' new ace. Premature? Not if you consider how the on-the-playoff-bubble Cards manipulated their rotation so Flaherty will be on turn to start their most important game of the year, whether that's the NL Wild Card Game or a must-win during the season's final series. The 22-year-old has earned the responsibility: He ranks among the NL rookie starter leaders in strikeouts (first), starts (second), innings (second), ERA (fourth), wins (first), fWAR (second) and WHIP (third).
Cubs: David Bote
An 18th-round Draft pick in 2012, Bote was pressed into duty when Kris Bryant was injured and has delivered in the clutch. On July 26 against the D-backs, he smacked a game-tying two-run homer with one out in the ninth. On Aug. 12 against the Nationals, Bote delivered a pinch-hit walk-off grand slam in the ninth. That blast helped teach people how to pronounce his last name (it's bow-tee). He hit another walk-off homer on Aug. 24 against the Reds and is the first Cub since Bryant in 2015 with two walk-off homers in one season. Bote has helped support the Cubs' motto to be versatile, starting at second, third, shortstop and in the outfield.
Video: David Bote's heroics vs. the Nationals this season
Pirates: Richard Rodriguez
Far from a household name, the 28-year-old rookie has become a vital part of Pittsburgh's bullpen in his first extended Major League opportunity. Signed as a Minor League free agent, Rodriguez entered the week with a 2.57 ERA, 1.08 WHIP and 79 strikeouts in 63 innings over 56 appearances. Rodriguez doesn't possess overwhelming stuff, but he's getting the job done with a 92.9-mph four-seam fastball he throws about 75 percent of the time plus a swing-and-miss slider.
Reds: Jesse Winker
Winker gets the nod despite having his season cut in half by injury. After a slow start, he found his stroke and some power. Overall, Winker batted .299/.405/.431 in 89 games but was slashing .362/.465/.554 in June and July before his year was halted by right shoulder surgery in his non-throwing arm to repair an injury that nagged him even in the Minors. Expected to be fully recovered by Spring Training, the 25-year-old with great plate discipline could be an even bigger offensive threat when fully healthy.
D-backs: Yoshihisa Hirano
While Hirano is technically a rookie as far as Major League Baseball is concerned, he certainly was not inexperienced coming into this season after spending 11 seasons pitching in Japan. The D-backs signed him to a two-year contract during the offseason, and he has more than met their expectations. Used primarily in a setup role through the first five months of the season, Hirano's effectiveness -- along with his unflappable makeup -- eventually got him moved into the de facto closer's role in September.
Dodgers: Walker Buehler
In any year not involving Acuna or Soto, the Dodgers' 24-year-old sensation would likely have been a favorite to win NL Rookie of the Year Award. Since his April recall from the Minor Leagues, Buehler was a steady presence through Clayton Kershaw's extended absence and has since cemented himself beside Los Angeles' ace at the top of the rotation, allowing two or fewer runs in 17 of his 21 starts. With the Dodgers embroiled in a tight divisional race, he has a 1.62 ERA since the start of August, and with his season mark at 2.74, he could become Los Angeles' first rookie starter to post an ERA under 3.00 with at least 20 starts since Hideo Nomo in 1995.
Video: COL@LAD: Buehler K's career-high 12 over 6 frames
Giants: Dereck Rodriguez
The son of Hall of Fame catcher Ivan Rodriguez is steadily establishing his own identity as a ballplayer as well as his candidacy for a respectable finish in the NL Rookie of the Year Award balloting. The 26-year-old, who converted to pitching from playing the outfield, demonstrated his consistency by pitching at least six innings and allowing two or fewer runs in nine consecutive starts. Despite their losing record overall, the Giants are 9-8 when Rodriguez starts. What makes Rodriguez's story even more remarkable is that he did not pitch above Double-A in Minnesota's farm system last year. San Francisco signed him as a Minor League free agent last November.
Padres: Franmil Reyes
Reyes was left unprotected in the Rule 5 Draft last December after leading all Padres Minor Leaguers in home runs in 2017. Thankfully for San Diego, he went unselected. Reyes' power is otherworldly, and he's made huge strides with his approach at the plate. The hulking 6-foot-5, 275-pounder is still a liability defensively. But he's grown into a legit middle-of-the-order game-changer.
Rockies: Ryan McMahon
Drafted as a third baseman but blocked at the hot corner by one Nolan Arenado, the 23-year-old McMahon made the Opening Day roster with eyes on the starting first-base job, but he was beat out by veteran Ian Desmond. After struggles at the plate and two extended Minor League stints, McMahon's .330 on-base percentage since his July 29 recall is fourth among Rockies. He has also shown a penchant for clutch homers -- four of his five 2018 long balls have come late in close games with Colorado trailing, including a memorable three-run walk-off shot against the Dodgers on Aug. 11.