CHICAGO — The Cubs felt good with rookie Cade Horton toeing the rubber in the series opener a pivotal, five-game series against the Milwaukee Brewers, a set that will very likely define the outcome of the National League Central division.

That optimism was dashed with two outs in the third inning when the rookie walked off the mound with the bases loaded with an injury as he was accompanied by trainer Nick Frangella. The team later announced Horton exited with a blister on his right middle finger.

He was replaced by left-hander Drew Pomeranz, who induced a groundout to end the rally. The injury was a blow for the Cubs, who will have to cover 18 innings across Monday’s doubleheader. The team has not announced a starter for Monday night’s contest against the Brewers.

Horton has been one of the Cubs’ best starters over the last month and a half. In his previous seven starts, Horton carried a 1.13 ERA in 40 innings, establishing himself as a mainstay in a Cubs’ rotation that had been plagued by injuries all season.

Frangella and Cubs manager Craig Counsell had checked on Horton earlier in the frame as the 23-year-old appeared to be dealing with a blister in his throwing hand. He had given up a solo shot to Brice Turang in the inning and then a double to Caleb Durbin after. He induced a ground out from William Contreras, walked Christian Yelich and then hit Andrew Vaughn before being removed from the game.

Horton was the Cubs’ first round pick in the 2022 draft and made his debut in May, posting a 3.08 ERA in 17 games (16 starts) and 87.2 innings this season. He has dealt with injuries in his past. Horton underwent Tommy John surgery in college at Oklahoma University, which limited him to 53.2 innings. Horton pitched just 34.1 innings in 2024 across Double-A and Triple-A as he dealt with a shoulder injury.