Given the evolution over the past decade that has changed the way front offices value young players, it's not all that surprising that we seem to be in an unprecedented era of baseball with regard to how many young players are dominating the game.
A recent Fangraphs article analyzed cumulative WAR totals over recent years and concluded this year's was the highest for players 25 and under, ever. In 2017, that group, at age 24, compiled the fourth-highest total ever, and in 2015 and '16, the 22 and 23-year-olds, respectively, had the highest-ever WAR for that age bracket.
"I think we're in the golden age of talent across the board, but our entire approach as an industry has changed, our entire belief system has changed, that's it's OK to have your youngest players be your best players," Astros manager AJ Hinch said. "I think teams are starting to trust the talent and youthful exuberance, in addition to wanting veterans sprinkled across the field, and the platform is there for the younger players to be the biggest stars."
As the four Division Series are set to being, clearly the kids -- all under the age of 25 -- are all right:
Astros: 3B Alex Bregman, age 24 (born March 30, 1994)
Chants of "M-V-P!" from Astros fans, normally reserved for Jose Altuve in the past couple seasons, shifted to Bregman in 2018, and for good reason -- the third baseman had a breakthrough year that was also historic. Bregman is the first player in Major League history to have 30 homers and 50 doubles in a season while playing the majority of his games at third base and, at 24, he's the youngest player in club history with a 30-homer season. The only other players in history who have had 50 doubles and 30 homers before turning 25 years old are Jose Pujols (2003-04), Alex Rodriguez (1996) and Lou Gehrig (1927).
In a year when a trifecta of All-Stars -- Altuve, George Springer and Carlos Correa -- missed ample time with injuries, Bregman was healthy and a stable force in an Astros' lineup that would have struggled to stay afloat without him.

Notable: Via Statcast™, Bregman finished the regular season with 150 hard-hit fly balls and line drives, second-most in the AL and fourth-most in the Majors. Bregman had a .601 average and slugged 1.432 on those hard-hit fly balls and line drives.
Braves: LF Ronald Acuna Jr., age 20 (born Dec. 18, 1997)
If there is anyone who defines why the Braves may have been just a tad ahead of schedule in returning to playoff contention, it's Acuna, a 20-year-old up-and-comer who should be in the center of Atlanta's core for years to come. Acuna is one of five players in baseball history to reach 26 homers in a season prior to his 21st birthday, and he's the 10th player to have 25 homers and 15 steals in his rookie season, and the first since Michael Trout in 2012. Acuna moved into the leadoff spot coming out of the All-Star break and took off, setting a franchise single-season record with eight leadoff homers.

Notable: Acuna is an exceptional power-speed threat. His 46.6 percent hard-hit rate was fifth-best among NL hitters this season, according to Statcast™, and his average sprint speed was 29.6 feet per second, putting him among the Top 20 fastest runners in the Majors.
Brewers: LHP Josh Hader, age 24 (born April 7, 1994)
What Hader has done this year, especially as a reliever, is historic. He owns the franchise record for strikeouts by a reliever, and he finished with a 46.7 percent strikeout rate -- becoming just the fourth pitcher ever to exceed 45 percent in a season with at least 50 innings pitched, along with Craig Kimbrel (for the Red Sox in 2017 and the Braves in '12) and Albertin Chapman (for the Reds in '14). Hader doesn't bounce back like some other, more established relievers, so the Brewers have developed a unique usage pattern where they pitch him in extended stints with multiple days of rest in between. How that translates through the postseason will make the Brewers one of the more interesting teams to watch.

Notable: Hader ended the regular season with a 36.4 percent whiff rate on swings vs. his four-seamer -- the best among relievers, according to Statcast™ (and he recorded 108 strikeouts with his fastball, 26 more than the next-closest relief pitcher, Chad Green). Not only that, the 54.5 percent whiff rate vs. Hader's slider was the fifth-best among relievers.
Dodgers: Walker Buehler, age 24 (born July 28, 1994)
Buehler has been one of the top pitchers all year and has been nails over the past two months. He posted a 0.99 WHIP in August, only to top that in September/October with a 0.77 mark. His 0.92 WHIP as a starter was the lowest among rookie pitchers with 20 or more starts in more than 100 years (since at least 1913), and Buehler limited opponents to a .193 batting average in his 23 starts. The right-hander has provided stability on an often injury-riddled pitching staff and, oh yeah, dominated the Rockies to clinch the NL West in a one-game playoff on Monday.

Notable: Buehler's 96.2-mph average four-seam velocity was sixth-highest among starters this season, and his 2,414 rpm average four-seam spin rate ranked 10th in that group. For reference, the MLB average spin rate on a four-seamer is just 2,263 rpm -- and a high-spin fastball is more likely to get whiffs.
Indians: SS Francisco Lindor, age 24 (born Nov. 14, 1993)
It's rare to talk about a player with so much postseason experience who is not yet 25, but if the Indians reach the World Series, it'll be a repeat performance for the Lindor, who was 22 two years ago when the Indians and Cubs met in an epic Fall Classic. Presumably, Lindor's star is still rising, though given what he's already accomplished, it's staggering to think he may be just getting started. Lindor and Trevor Story this year became the first shortstops in history with 35 or more homers, 40 or more doubles and 20 or more stolen bases in the same season.

Notable: According to Statcast™, Lindor led the American League with 226 hard-hit balls overall this season and was tied for third-most in the Majors. Of those hard-hit balls, 152 were line drives or fly balls -- the most hard-hit line drives/fly balls of any AL hitter, and third-most in MLB. Lindor was also tied for fifth in the Majors, with Mookie Betts, with 36 extra-base hits vs. breaking/off-speed pitches.
Red Sox: OF Andrew Benintendi, age 24 (born July 6, 1994)
Benintendi, a mere three years out of college, has proved to be a mainstay in a steady lineup that has contributed mightily to Boston's historic season. The Red Sox's first-round pick in 2015, Benintendi exceeded his 2017 totals in hits, runs scored, doubles and stolen bases -- totals which had earned him a runner-up finish for AL Rookie of the Year -- and he also tied for the Major League lead in outfield assists.

Notable: Benintendi hits it all over the field -- he had 60 opposite-field hits this season, the second-most of any hitter in baseball.
Rockies: RHP German Marquez, age 23 (born Feb. 22, 1995)
In his start against the Phillies last Wednesday, Marquez tied a modern Major League record by striking out the first eight batters he faced, and in doing so, also broke the club's single-season strikeout record. He finished with 230 on the year, and he has, in recent times, proven to be a force at Coors Field. In his past seven home starts, Marquez has allowed 10 earned runs over 47 1/3 innings, for a 1.90 ERA, and he's been one of the top pitchers in baseball since the All-Star break. Over his final 17 starts of the regular season, he went 9-3 with a 2.47 ERA, holding opponents to 31 earned runs over 113 innings.

Notable: Marquez recorded 130 strikeouts on curveballs in the regular season, second-most of any pitcher behind Zack Godley, who had 134. Marquez's slider also became a key part of his repertoire in the second half -- he totaled 100 strikeouts on his curve and slider after the All-Star break, the most breaking-ball strikeouts of any pitcher in the second half.
Yankees: 3B Miguel Andujar, age 23 (born March 2, 1995)
Andujar led all rookies in hits (170), doubles (47), RBIs (92) and multihit games (53) and tied for the lead in home runs (27) -- and he's proven time and again that not only is he talented, he's clutch. Of his 27 homers, four tied the game and nine gave the Yankees the lead. He's one of three Yankees rookies to hit at least 27 homers in a season, joining Aaron Judge, who hit 52 last year, and Joe DiMaggio, who recorded 29 homers in 1936.

Notable: Andujar, according to Statcast™, notched 82 hits off breaking and offspeed pitches, the fourth-most of any hitter in baseball. Forty-one of those were extra-base hits, third-most in baseball, only one behind NL MVP candidates Story and Javier Baez.