William Contreras' continued aggressive ABS challenge use was key to Brewers' NL pennant win

William Contreras has caught every inning of the Milwaukee Brewers' 2026 postseason run. That's not especially uncommon for starting catchers during the playoffs, and for those familiar with Contreras' iron-man mentality, it's especially unsurprising that the Brewers' All-Star backstop has been behind the dish for every pitch this October.

While his performance at the plate is rightfully gaining most of the attention -- Contreras has a 1.157 OPS with three homers and five RBI in eight games during the postseason -- the defensive value that the Brewers' catcher has produced during the playoffs should not be overlooked. Contreras, who was among the best defensive catchers in baseball during the 2026 season, in large part due to his control of opponents' running game, but was surprisingly not named a Gold Glove finalist this year, has continued to impress with his arm in the postseason. He's thrown out two would-be base-stealers while allowing just two total stolen bases in the Brewers' eight playoff games.

However, perhaps the most valuable part of Contreras' defensive game during the postseason has been his success with the ABS challenge system. The ABS system, which was implemented at the start of the regular season, wasn't necessarily Contreras' strong suit for a majority of the regular season. The Brewers catcher had a 57% success rate on ABS challenges from behind the dish during the regular season, which ranked 45th out of 77 catchers with more than 20 challenges this year.

Despite his mediocre success rate, Contreras was by far the most aggressive challenger in baseball. The Brewers' backstop challenged 185 calls throughout the regular season, and the second-most frequent challenger, Tyler Stephenson of the Cincinnati Reds, challenged just 136 calls. Some of that is due to the fact that Contreras caught more innings than any other backstop in MLB this year, but there's no denying the Brewers' catcher wasn't tentative with his use of the ABS challenge system, even if the situation didn't necessarily call for it.

Thankfully, for the Brewers' sake, Contreras' challenge success rate improved as the season went on. In September, Contreras posted a 75% success rate from behind the dish. Additionally, while Contreras' overall success rate was rather pedestrian, he did rank first in run value gained through successful challenges (16.4), in large part due to the fact that he gained 25 strikeouts (2nd in MLB) and eliminated nine walks (5th in MLB) with the ABS system. That, however, was again the result of his aggressive use of the challenge system as Contreras also led the league in run value cost due to unsuccessful challenges.

Contreras' aggressive ABS use has continued into the postseason, and while there's certainly been some questionable decisions from the All-Star backstop -- an unsuccessful challenge on the first pitch of Game 3 of the NLDS stands out -- overall the Brewers' have benefitted from their catchers' challenges thus far in October.

William Contreras has remained aggressive with the ABS challenge system in the postseason, and it's working

Despite playing in just eight postseason games, Contreras has already challenged 20 calls from behind the plate. For reference, Patrick Bailey, who has already played 10 games during the postseason, has the second-most challenges during the postseason with 14. Contreras is 12 for 20 in those ABS challenges, which isn't the highest success rate, but he has generated the most run value with the challenge system of any catcher in the postseason this year.

Additionally, Contreras' overall success rate during the postseason was weighed down by a pedestrian performance in the NLDS, but in the NLCS, the Brewers' backstop was excellent with the ABS system. Contreras went 8 for 11 on challenges in the Brewers' four-game sweep of the Dodgers, good for a 73% success rate that undoubtedly played a role in the series. On top of that, given the instances in which Contreras used his challenges, his run value gained was 0.8 throughout the series, while his run value cost with the ABS system was exactly 0.0.

Contreras' aggressive use of the ABS challenge system can certainly be frustrating at times -- see the reference to Game 3 of the NLDS above. However, according to the numbers, this strategy has made Contreras the most valuable ABS challenger of any catcher in the postseason.

There's perhaps a negative side effect to this strategy -- the Brewers' offense has made just seven total challenges during the postseason, and according to run value above average, they have been the worst challenging offense in October. Undoubtedly, Contreras' aggressive use of the ABS system could make the Brewers' hitters more hesitant to tap their helmets. However, the flip side of that argument is that Milwaukee's offense was never aggressive when it came to the ABS system, so perhaps Contreras is just taking advantage of that conservative approach and using the otherwise wasted challenges on the defensive side of the ball.

Whatever the agreement between Contreras and the Brewers' hitters is, Milwaukee's use of the ABS system, which was a hot topic throughout the regular season, is working in the playoffs. Contreras has hit his stride, and his overturned calls in the NLCS were a key part of the Brewers' sweep of the Dodgers. Should that success continue in the World Series, it could be a key part of the Brewers' quest for their ultimate goal.

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