Sabathia appeared to be laboring in the third inning against the Cleveland Indians when he struck out Yan Gomes. After a 91 mph fastball, manager Joe Girardi and athletic trainer Steve Donohue raced out of the dugout to talk to Sabathia.
Following a brief conversation, Sabathia walked off the field.
Sabathia said he is normally able to push through the pain. In fact, most of the season, as a crutch, he said he has alternated his landing to protect the knee. Sabathia said he recently decided to forget about that, and he saw his velocity rise from the low 90s to as high as 94. He had been a little more effective of late, too.
"I was just saying, 'Screw it,'" Sabathia said. "Today, though, I couldn't take it."
An MRI didn't reveal much new except a "bad knee," Sabathia said.
Sabathia had fluid drained right before the All-Star break. He had a cortisone shot earlier in the week to try to deal with the new discomfort.
"I'm guessing it is a DL [stint], off the bat," Yankees general manager Brian Cashman said.
With Michael Pineda to return from the DL on Wednesday, the Yankees were planning to go to a six-man rotation. Even if Sabathia misses an extended amount of time, they still could go to a six-man rotation, as Bryan Mitchell -- who has a broken nose -- is going to pitch in a simulated game early this week. Mitchell could be stretched out as a starter to replace Sabathia.
It has been a frustrating year for Sabathia, who entered Sunday with a 4-9 record and a 5.24 ERA. Sabathia, 35, missed most of last year because of right knee surgery, going 3-4 with a 5.28 ERA.
Sabathia had arthroscopic debridement surgery a little more than a year ago, with some thought that it could end his career.
"It is super frustrating because it is still in there," Sabathia said. "The last couple of starts, you guys have seen. It is just frustrating I can't do it every time."
Sabathia is owed $25 million for next season and, as long as he doesn't hurt his shoulder, $25 million for 2017.
"I want to see how I can fix it," Sabathia said.