Chicago Bulls head coach Billy Donovan is optimistic Lonzo Ball's latest knee surgery will address his ongoing discomfort but refused to put a timeframe on his return.

Bulls guard Ball on Wednesday underwent a second arthroscopic surgery on the knee which has seen him sidelined since January.

Ball revealed on Tuesday that he is still unable to run or jump due to the pain in his left knee.

Donovan said Ball's operation "went well", although he was cautious to commit to any timeline on a return to practice or playing.

"You always try to stay optimistic that this will get resolved and he'll be fine," he said.

"But until he gets back and gets into the situations that were causing him pain, to see how he responds in being back in those situations, we'll find out more.

"I don't know how long it will take before he can actually start the rehab process."

Prior to Wednesday's procedure, the Bulls had announced they would re-evaluate Ball's status in four to six weeks, meaning he is unlikely to play in the NBA until November at the earliest, given he has not played since January 14.

"You've also got a player that's been out for nine months," Donovan said. "It's not like in three weeks, the surgery is a success, you can just throw him back out there and play.

"We haven't even gotten to the point if this all goes well with the rhythm, timing, the flow, catching up.

"He's had no competitive play since [January]. So that's a whole other scenario of when he could actually get back."

The Bulls are due to open their NBA campaign against the Miami Heat on October 19.

Ball, who was taken with the second pick overall in the 2017 NBA Draft, moved to the Bulls from the New Orleans Pelicans in August last year, averaging 13.0 points, 5.4 rebounds and 5.1 assists across 35 games in the 2021-22 season.