Each summer, contenders around the Major Leagues scramble to add players prior to the non-waiver Trade Deadline with hopes of bolstering their rosters for a run at October.
Both of the 2018 World Series teams did exactly that. The Red Sox found a gem in Steve Pearce, who went on to become the World Series Most Valuable Player after playing a critical role in their championship run. The Dodgers swung a huge trade to acquire superstar shortstop Manny Machado from the Orioles, and Machado had a major impact on their run to a second straight National League pennant.
Even teams that miss out on those opportunities can still bring in key pieces until Aug. 31 -- the last date that a team can add players who will be eligible for postseason rosters (see Andrew McCutchen and Josh Donaldson in 2018).
For all the hype that surrounds these in-season trades, how many of them have actually helped teams play deep into October and reach baseball's biggest showcase?
We combed through decades' worth of deals to pick out 14 players who made a difference en route to the World Series.
Steve Pearce, 2018 Red Sox
Pearce started the 2018 season a Blue Jay. He ended it as the MVP of the Fall Classic for the Red Sox, making him just the second midseason acquisition to ever win World Series MVP, along with the Mets' Donn Clendenon in 1969. On a Boston team led by a duo of superstars in Mookie Betts and J.D. Martinez, it was Pearce -- acquired from Toronto on June 28 for Minor Leaguer Santiago Espinal -- who came through with some of Boston's biggest hits of the World Series.
In the Red Sox's clinching Game 5 win over the Dodgers, Pearce homered twice to bookend the scoring. His first homer, off Clayton Kershaw, gave the Red Sox a 2-0 lead in the first inning, and the second pushed their lead to 5-1 in the eighth, putting the series away. Those homers came just a day after Pearce crushed a game-tying blast off Dodgers closer Kenley Jansen in the eighth inning of Game 4, followed by a bases-clearing double that broke the game open in the ninth. Not bad for someone who was brought in mainly to give the Red Sox a platoon advantage against left-handed pitching.
"We're happy to have Steven join us," president of baseball operations Dave Dombrowski said when the Red Sox first got Pearce. "He's a proven Major League player. Very quality right-handed hitter. Hits left-handed pitching very well. The type of guy we've been trying to add to the lineup vs. left-handers."
Justin Verlander, 2017 Astros
The Astros made a stunning move, trading three prospects to the Tigers for the former AL MVP Award and Cy Young Award winner, adding Verlander in the final minutes -- seconds, actually -- before the Aug. 31 deadline.
"I think he'll add a dimension we don't have," Astros owner Jim Crane said at the time. "He's pitched well his whole career and has been pitching well lately. I think he'll add a dimension in the playoffs, hopefully, when we get there. I think it's great for the team. I think the players will be excited and fans will be excited."
Verlander earned ALCS MVP Award honors and finished 5-0 with a 1.06 ERA in five September starts before posting a 4-1 record and 2.21 ERA in six October outings to help the Astros to their first World Series title.
Andrew Miller, 2016 Indians
When the Yankees decided to become sellers before the 2016 non-waiver Trade Deadline, the Indians seized the opportunity to deal for Miller, sending four Minor League prospects to New York.
Miller bolstered an already solid bullpen, giving manager Terry Francona a plethora of weapons to use in a variety of ways.
"We're getting one of the very elite relievers in all of baseball," Francona said.
Miller proved to be just that, pitching to a 1.55 ERA in 26 regular-season appearances. The left-hander recorded at least four outs in each of his 10 postseason appearances, earning ALCS MVP Award honors against the Blue Jays, as the Indians reached their first World Series since 1997 before losing in seven games against the Cubs.
Yoenis Cespedes, 2015 Mets
The Red Sox acquired Cespedes in a 2014 non-waiver Trade Deadline deal that sent Jonathan Lester to the Athletics, but the Cuban slugger would be traded again that winter to the Tigers. Only seven months after joining Detroit, Cespedes was traded to the Mets on July 31.
"His presence in the lineup and on the team will raise the energy level, and I hope it raises the energy level in the dugout and in the stands," Mets GM Sandy Alderson said after making the deal. "This is a player that can have a big impact, both in terms of on the field and how the team is perceived."
Cespedes mashed opposing pitchers after arriving in New York, blasting 17 home runs with 44 RBIs and a .942 OPS in 57 games through the end of the season. He homered twice in the NL Division Series against the Dodgers, then drove in three runs in the four-game NLCS sweep of the Cubs. The Mets lost a five-game World Series against the Royals, but Cespedes re-signed with New York after the season, making the NL All-Star team in 2016.
Benjamin Zobrist, 2015 Royals
The Royals were aggressive at the 2015 non-waiver Trade Deadline after reaching the World Series the previous season, acquiring Ben Zobrist from the Athletics for Sean Manaea and Aaron Brooks -- two days after trading three Minor Leaguers to the Reds for Johnny Cueto.
"Obviously, they have played well and they already have a great club, and then they have the addition of Johnny Cueto," Zobrist said after his deal. "There should be a lot more wins coming. I'm super excited about this. They are already a good team. I just have to try and not screw it up."
Zobrist hit .303 with two homers, six RBIs and an .880 OPS in 16 postseason games as the Royals won their first World Series title in 30 years. Cueto made four starts in October, pitching a pair of gems, including a complete-game victory in Game 2 of the World Series against the Mets.
Jake Peavy, 2013 Red Sox, '14 Giants
The Red Sox acquired the veteran Peavy in a three-team deal on the day before the non-waiver Trade Deadline in 2013.
"He's an intense competitor," Boston GM Ben Cherington said. "I think he'll fit in nicely with the group that we have."
Peavy went 4-1 despite a 4.04 ERA in 10 regular-season starts, then started one game in each postseason series as the Red Sox won their third World Series since 2004.
The following summer, the Red Sox dealt the right-hander to the Giants five days before the Trade Deadline. Peavy thrived in San Francisco, going 6-4 with a 2.17 ERA in 12 starts before winning his San Francisco postseason debut with 5 2/3 scoreless innings against the Nationals. He didn't pitch particularly well in his other three postseason starts, but Peavy picked up his second straight World Series ring nonetheless.
Cliff Lee, 2009 Phillies and '10 Rangers
With an eye toward defending their World Series crown, the Phillies made the biggest move possible, trading for the reigning AL Cy Young Award winner two days before the non-waiver Trade Deadline.
"Obviously the Phillies are the defending world champions, they're a good team, and they're in first place," Lee said. "Honestly, it's an honor, and I look at it as a good thing. If other teams are wanting me and are willing to trade some of their key players and future players for me, it's a compliment."
The Phillies acquired Lee and Louis Francisco from the Indians, sending four Minor Leaguers back to Cleveland, including Carlos Carrasco. Lee went 7-4 with a 3.39 ERA in 12 starts following the trade, then pitched brilliantly during the postseason, going 4-0 with a 1.56 ERA in five starts. The Phillies won all five games started by Lee in the playoffs, including two against the Yankees in the World Series, but Philadelphia lost the Fall Classic in six games.
Lee was traded to the Mariners that winter, then again the following July, as the Rangers bolstered their postseason hopes. Lee pitched to a 0.75 ERA in three starts over the first two rounds of the playoffs, helping the Rangers get to their first World Series in franchise history before losing to the Giants.
Orlando Cabrera, 2004 Red Sox
A four-team trade shook the baseball world at the July 31 non-waiver Trade Deadline in 2004. The Red Sox traded the face of the franchise -- Nomar Garciaparra -- to the Cubs, receiving Cabrera from the Expos and Doug Mientkiewicz from the Twins.
"We lost a great player in Nomar Garciaparra, but we've made our club more functional," Boston GM Theo Epstein said after making the deal. "We weren't going to win a World Series with our defense."
Cabrera had two solid months after replacing Garciaparra, hitting .294 with six home runs and 31 RBIs in 58 games while playing a stellar shortstop. Cabrera struggled in the ALDS against the Angels, but he starred in the next round against the Yankees, hitting .379 and playing a major role in Boston's unprecedented comeback from an 0-3 deficit.
Cabrera was one of five players to drive in three or more runs in Boston's Fall Classic sweep of St. Louis. The last out was caught by Mientkiewicz, making him part of Red Sox lore forever.
Larry Walker, 2004 Cardinals
The Cardinals already had the best record in the NL when the July 31 non-waiver Trade Deadline passed, but St. Louis strengthened its lineup a week later by trading for Walker, a five-time All-Star. The 37-year-old Walker waived his no-trade clause, eager for a chance to play in the World Series for the first time in his 16-year career.
"It's a good thing I am going to a team that is 31 games over .500," an emotional Walker said the day he joined the Cardinals. "It is tough not to be happy about that. They are going to the playoffs and have a chance to win the World Series."
Walker hit .280 with 11 home runs and 27 RBIs in 44 regular-season games, then hit .293 with six homers and 11 RBIs in 15 postseason games. However, Walker's first and only World Series appearance was short-lived, as the Red Sox swept the Redbirds, ending Boston's legendary 86-year World Series drought.
Aaron Boone, 2003 Yankees
One look at Boone's statistics with the 2003 Yankees would lead you to believe his stay in the Bronx wasn't very impactful. Think again.
Acquired at the July 31 non-waiver Trade Deadline for Brandon Claussen, Charlie Manning and cash considerations, Boone took over at third base after the Yankees dealt Robin Ventura to the Dodgers on the same day. Boone hit .254 with six home runs and 31 RBIs in 54 games, but struggled in the ALCS against the Red Sox.
Manager Joe Torre benched Boone for Game 7, but he would later come into the game as a pinch-runner in the eighth, setting up the most famous swing of his career. His 11th-inning walk-off home run against knuckleballer Tim Wakefield clinched the pennant for New York, sending Yankee Stadium into a frenzy. The Yankees fell to the Marlins in a six-game World Series, but Boone's legacy in the Bronx was cemented forever.
"Not a week goes by that I'm not reminded of how big the New York Yankees are or how big their reach is," Boone said last winter after being introduced as the Yankees' new manager. "I've had hundreds of stories told to me, too, about where people were or what side of the ledger they were on."
David Justice, 2000 Yankees
The Yankees had already won three World Series in a four-year span from 1996-99, but the 2000 team spent most of May and June fighting to stay atop the AL East. Enter Justice, a former NL Rookie of the Year Award winner and three-time All-Star, for whom the Yankees traded Zach Day, Ricky Ledee and Jake Westbrook to the Indians.
"I'm stunned," Justice said after being traded. "But business is business. That's the game we play. I'll go there and play hard like I do everywhere. I've never really felt comfortable there as an opposing player."
He certainly looked comfortable after slipping into his new pinstripes. Justice hit .305 with 20 home runs, 60 RBIs and a .977 OPS in 78 games for the Yankees, but his biggest impact came in October. The 34-year-old hit two homers and drove in eight runs against the Mariners to win ALCS MVP Award honors, as the Yankees went on to win their third straight World Series title.
David Cone, 1992 Blue Jays
The Mets didn't move Cone prior to the July 31 non-waiver Trade Deadline in the summer of 1992, sitting only four games out of first place in the National League East. But a 4-15 start to August blew their season apart, prompting New York to trade its ace -- an impending free agent -- to the Blue Jays on Aug. 27 for Jeff Kent and a player to be named later, who turned out to be Ryan Thompson.
"I'm here on a great team in a great organization in a city that's really hungry to win, and a team that has a good chance to win," Cone said at the time. "I'm very fortunate to be here."
Cone went 4-3 with a 2.55 ERA down the stretch for Toronto, which held off the Brewers and Orioles to win the AL East title. Cone pitched well in two of his four postseason starts, including a Game 2 gem in the ALCS against the Athletics. His World Series ring that season would be the first of five in his career.
Rickey Henderson, 1989 A's and '93 Blue Jays
Henderson had already long established himself as the game's best leadoff hitter by 1989, making eight American League All-Star teams in his first 10 seasons. When Oakland -- the team with which he started his career -- reacquired him from the Yankees for Greg Cadaret, Eric Plunk and Luis Polonia on June 21, 1989, Henderson added a huge presence to the top of an already ferocious lineup.
"There were rumors that I'd be traded, and then they came to me and asked if I would take a trade," Henderson said at the time. "Oakland was the only place I knew I'd like to go."
Henderson took off upon returning to the East Bay, batting .294 with 72 runs scored and 52 steals in 85 games. He went on to win American League Championship Series MVP honors, hitting .400 with two homers, five RBIs and eight steals against the Blue Jays. He then batted .474 in the Bay Bridge World Series, helping the Athletics sweep the Giants.
Henderson would be the focal point of another midseason deal four years later, as the Blue Jays acquired him on July 31, 1993. The Athletics received Steve Karsay and a player to be named later, who turned out to be Jose Herrera, from Toronto. While Henderson hit only .215 in 44 games after the trade, he played a role in the Blue Jays' second consecutive World Series title that October.
Lou Brock, 1964 Cardinals
Brock was having an off year in 1964, batting .251 with two home runs, 14 RBIs and 10 stolen bases in 52 games when the Cubs traded him to the Cardinals (at the former June 15 deadline) with Jack Spring and Paul Toth for Ernie Broglio, Doug Clemens and Bobby Shantz.
The reaction to the deal wasn't positive from the Cardinals' side at the time, with future Hall of Famer Bob Gibson even calling it "a dumb trade."
Brock, who turned 25 three days after the trade, hit .348 with 12 home runs, 44 RBIs and 33 steals in 103 games for St. Louis, leading the Cardinals to the World Series after the club had been as many as 11 games out of first place in late August. He hit .300 with a home run and five RBIs in the seven-game Fall Classic against the Yankees, winning the first of his two World Series rings.
The left fielder went on to play 15 more seasons for the Cardinals, making six All-Star teams and putting together a Hall of Fame career in the process.
Mark Feinsand, executive reporter for MLB.com, has covered the Yankees and MLB since 2001 for the New York Daily News and MLB.com.