The 31-year-old Wallace, now in his 13th NBA season, had an MRI scheduled Thursday to re-examine bone spurs in his left ankle that the team planned to operate on after the season. Wallace asked to check out a bothersome left knee at the same time and discovered that he has a torn meniscus that needed more immediate attention.
Wallace, who despite the nickname "Crash" has never undergone surgery during his NBA career, said he expects to be sidelined for two to four months after surgery, but hopes to be ready for the start of training camp next season.
"I'm very disappointed, just the simple fact that the injury, not knowing how long I've been playing with it and what was going on," Wallace said. "It was just a pain that kinda felt different in my knee. I'm disappointed to end my season this way, just when it felt like I was starting to play at a pretty high level."
Wallace averaged 5.1 points, 3.7 rebounds and 2.5 assists over 58 appearances, including 16 starts, most of which came recently in place of sidelined shooting guard Avery Bradley. In his final appearance on Wednesday, Wallace put up 12 points and 10 rebounds in a win over the Hawks.
"I feel bad for him. I told you many times: Gerald's a warrior, he plays through anything and everything," Celtics coach Brad Stevens said Friday. "Literally, anything and everything is what we're learning."
Wallace initially struggled with being traded from Brooklyn to a rebuilding Boston squad this summer and didn't report until right before the start of training camp. He emerged as a veteran leader who wasn't afraid to voice his opinions.
"[The 2013-14 season has] been great. The experience has been fun," Wallace said. "Losing sucks, it always does. I felt like we're a lot better than what our record shows. We've had some ups and downs, some learning curves, not only from the players, but from the coaching staff as well. Everybody learning everybody was an adjustment. But I think for the most part, it's been a great season."
Wallace has two seasons and $20.2 million remaining on his current contract.