Rookie Impact in the Postseason

Corbin Carroll taking a swing; CC by License 2.0

People interested in understanding their favorite team’s farm system often lose sight of what matters most in regards to their favorite prospects… on-field performance. All the prospect hype is exciting, but none of the hype matters until a player makes it under the bright lights. Here’s a look at the most impactful rookies on every championship series team. Most of these teams leaned on rookies to contribute and have had rookies play an integral role to their postseason success. When looking at the four teams that made it to their respective LCS this postseason, it’s clear that the help they’ve gotten from their farm systems helped push them closer to the finish line.

*Position players are listed with their regular season and postseason wRC+*

*Pitchers are listed with their regular season and postseason FIP*

Corbin Carroll, 133/118

It’s hard to believe that the star from game 7 of the NLCS, Corbin Carroll, is still a rookie. He’s been the heart and soul of this Diamondbacks team since April and has played the most influential role in their success this season. There are few players in the entire postseason that are as impressive as Carroll. He is a true five tool guy, a term that I don’t like to throw around often. Carroll gets on base, has the ability to change the game with his power, is always solid in the outfield, and is a nuisance to pitchers while he’s on the bases. He’s the complete package and a perfect example of the prospect hype living up to reality.

Brandon Pfaadt, 5.18/2.15

While Brandon Pfaadt deserves a lot of credit for his postseason dominance, so does Mike Hazen, Torey Lovullo, and the entire Arizona Diamondbacks staff. Pfaadt had a track record of success throughout the minor leagues and became a data darling with his impressive slider. He worked 96 regular season innings and wasn’t very impressive. Hitters seemed able to pick up the slider easily and were consistently making hard contact as a result of this. Despite the lack of big league success, the coaching staff trusted Pfaadt to be a part of their playoff rotation, a somewhat surprising move that has surely paid off. He’s done a great job limiting walks, something that becomes even more critical on the postseason stage. It was clear on Tuesday night that the playoff excellence carried forward as Pfaadt went 4 innings with 2 ER and 7 Ks in a critical game 7.

Johan Rojas, 109/-33

The Phillies are probably the least rookie reliant team of any of the teams that made it to the league championship series, and Rojas is the only player I could find that really qualifies for this list. He has stepped into a platoon role and established himself as a viable bottom of the lineup option as well as a superb defensive player. Rojas is the type of player that becomes more valuable in the playoffs than he does in the regular season. He’s a constant threat to swipe a bag and can take away hits in centerfield. Even in games that he doesn’t start, Rojas is valuable late in the game as a pinch runner or defensive replacement. He flies under the radar with all the starpower in the Phillies lineup, but Johan was an important piece of this team’s success.

Josh Jung, 110/138

The Rangers started the year with very few holes, but the biggest question surrounding this Rangers squad was their third base situation. Jung stepped up and filled the void very well. He has been a steady presence at the hot corner and played well enough to be the first rookie all-star starter in the history of the Rangers. Jung might not match the flashiness of an Adolis Garcia or the consistency of Corey Seager, but he lengthens the Rangers lineup considerably and is a vital part of this team looking ahead to the World Series.

Evan Carter, 180/174

The Rangers started hot this season and looked like they’d end up running away with the AL West. A long losing stretch and an inevitable Houston hot streak made it an extremely interesting race. After posting video game numbers in the minors all season, Carter was called up on September 8th and provided the spark that Texas needed. He’s established himself as a 3 hole hitter and has flashed plate discipline that very few rookies are able to match. Carter has struggled against lefties, but his performance against righties has made him the most impactful rookie in the entirety of the postseason.

Yainier Diaz, 127/-74

Don’t pay any attention to the -74 wRC+, Diaz only had 14 plate appearances in the postseason, much to many Astros’ fan dismay. Maldonado is part of the core of this historic Astros team, but it’s clear that it’s time for Diaz to take over. In close to 400 plate appearances this season, Diaz was better than anyone could have expected. He was one of the best hitting catchers in the entire league. A 2 percent walk rate isn’t going to play, so the plate approach is going to need a significant overhaul. However, the talent is clear and Diaz seems likely to assume the starting catching duties next year.

Hunter Brown, 4.37/3.83

There were high expectations for Brown entering this season, especially after his impressive showing in his 2022 cup of coffee. It’s fair to call his 2023 a bit of disappointment. In a starting role and swingman role, he was ineffective. He was relegated to a bullpen role for the postseason and has been successful in limited action. The Astros are still high on Brown internally and he’s sure to start next year in the Astros rotation.

While these teams have relied on their rookies to various degrees, all of them have been helped at some point by an infusion of youth. Postseason baseball has always had an all hands on deck approach and that will only be amplified as the playoffs get longer and longer. Keep an eye on top prospects this offseason to see what players might get called up and be postseason contributors next year.