The Chicago Cubs don't yet know the extent of starting pitcher Jameson Taillon's hamstring injury. But one thing all parties seem to be certain of: the veteran right-hander is headed for the injured list.

The 34-year-old Taillon left with one on and none out in the second inning of the Cubs' Sunday night game against the visiting San Francisco Giants. After walking Matt Chapman on six pitches to start the second, Taillon summoned the trainer to the mound.

Taillon was pulled from the game, walking gingerly into the dugout and down the stairs toward the clubhouse. He was replaced by Javier Assad, who pitched 6 1/3 scoreless innings in a game ultimately won by the Giants, 2-1 in 10 innings.

"It's a left hamstring strain," manager Craig Counsell announced after the game. "Imaging tomorrow ... it's an IL. We'll get more information tomorrow (regarding) severity and maybe an idea of a timeline."

For his part, Taillon was optimistic about a long-term prognosis but resigned to the fact that he will be missing some time.

"I don't think it's crazy," Taillon told reporters after the game. "Like, I'm walking around and moving around. Obviously, it will be an IL stint but, hopefully, we can keep the arm conditioned and moving around. ... But I don't it's surgical or anything like that. I'm getting an MRI tomorrow and we'll know more."

Taillon entered the game sporting a 2-5 record and 5.19 ERA in 67 2/3 innings across 13 starts.

In his fourth season with Chicago, Taillon is 33-30 with an ERA just above four in 94 games (93 starts) with the Cubs.

He is 84-65 with a 3.94 ERA in 10 seasons with the Cubs, Pittsburgh Pirates (2016-19) and New York Yankees (2021-22).