Hill had a 4-0 lead through four innings before exiting during a three-run fifth. The Cubs would go on to rally for a 6-5 win.
"I feel stupid for staying in, to be honest with you, stubborn," Hill said after the game. "Put us in a really bad position, and unfortunately, that falls on me, my stubbornness staying in and wanting to compete."
Hill appeared to be shaking his left leg at one point in the fifth and was visited by an athletic trainer. Hill exited after hitting Patrick Wisdom to load the bases with two outs.
Hill said he felt a "pop" in the knee on a breaking ball in the fifth inning and in the moment thought it was something he could pitch through. He mentioned his past MCL issues, most recently in 2019, and said the team would hopefully know more about the extent of the injury in the coming days.
Hill, who debuted with the Cubs in 2005, gave up three runs and three hits in 4⅔ innings. He walked four and struck out three. Hill said he "felt great'' prior to the fifth.
"Unfortunately, I put us in a tough position, and that's what makes me sick to my stomach," he said. "But overall, before that point, the ball was coming out well.''
The Associated Press contributed to this report.