MIAMI -- The Yankees have seen Albertin Chapman manage his left knee tendinitis without complaint for most of the season, which is why manager Aaron Boone said that he was concerned when the left-handed closer effectively removed himself from an appearance on Tuesday against the Marlins.Chapman threw only six pitches

MIAMI -- The Yankees have seen Albertin Chapman manage his left knee tendinitis without complaint for most of the season, which is why manager Aaron Boone said that he was concerned when the left-handed closer effectively removed himself from an appearance on Tuesday against the Marlins.

Chapman threw only six pitches before leaving the field in the 12th inning, complaining of increased discomfort in his knee. With Player Page for David Robertson also ailing, Tommy Kahnle polished off the Yankees' 2-1, 12-inning win in place of Chapman, who is expected to undergo an MRI exam on Wednesday.

"Tonight was more than usual; the pain was just more," Chapman said through an interpreter. "That's why I decided to call the trainers out. It was more than what I've encountered lately. It's worrisome, but we've got to wait until tomorrow and see what happens."

Boone said that Chapman's discomfort is in the same spot that prompted his removal from a July 8 game against the Blue Jays in Toronto, which also forced Chapman to bow out of the All-Star Game. Chapman has said that he has been battling the knee issue since May.

"Previously, I've been able to pitch with it, to manage it," Chapman said. "When I got out there, it was just more than usual. Maybe too much pressure on the knee, I don't know. … The pain was more than usual.

"The discomfort is constant. When I'm pitching and I use my legs and I put more effort into my legs, my knees, then you feel it more."

Chapman's fastball averaged 96 mph in Tuesday's appearance, his lowest since 2013. He is 3-0 with a 2.11 ERA and 31 saves in 50 appearances this year.

"I'm concerned about it just because really virtually every other time he's been able to work through it," Boone said. "For him to call attention to it, that has me concerned. You kind of hope for the best tomorrow. Hopefully we can get him on the road to recovery."

Boone said that his bullpen hierarchy had already been disrupted when Robertson reported a tender spot near his throwing shoulder in pregame warmups. Boone said that he is "not overly concerned" about Robertson, who said that he should be able to pitch on Wednesday if needed.

"It's nothing that doesn't come throughout the season," Robertson said. "I was fortunate to get three days off in a row without pitching in a game, then came down here and played catch today. Just felt like I wasn't quite 100 percent, and I didn't want to go out there and not be the guy that they expect me to be. … I wish I could've been there to help them out, and hopefully [Wednesday] I'll be ready to go."