Discussing injuries to his three starters -- Garnett, Paul Pierce (right knee infection) and Rajon Rondo (sore left hamstring) -- prior to Saturday night's game with the Toronto Raptors at TD Garden, Rivers said Pierce and Rondo were the closest to returning, with Garnett looking at a three-week recovery window after being kicked in his surgically repaired knee twice during a three-game trip this past week.
"KG's still 10 days, maybe, I don't know," said Rivers. "I have no idea, I honestly don't. There is some history with hyperextended knees that we kind of know that it takes at least two weeks, sometimes three. We know it won't be longer than that, but we don't know how quickly. There's a history there -- not with [Garnett] -- but with league history."
Rivers continued to stress that Garnett's injury should not be a long-term issue.
"It won't be that long," Rivers said after Friday's practice. "When I did this, I looked at the schedule and the days off, and I thought this was the time to do it."
As for Rondo and Pierce, Rivers was more optimistic they would return during the Celtics' upcoming three-game road trip.
"Rondo and Paul would be first in line," said Rivers. "I think Rondo will play in the Miami game [on Wednesday].
"I think Paul is fifty-fifty, he'll try to practice on Monday and we'll see how it feels. With infections, we don't know how to treat that, nobody [here] has ever had that. We'll find that out. We don't know what will happen once he practices. It could swell, it could feel great. We just have to wait and see."
Pierce spoke to the media Saturday for the first time since undergoing what he detailed as a pair of procedures to drain fluid from his right knee, including a previously undisclosed operation on Christmas Day.
"I'm getting better, feeling pretty good," said Pierce. "Right now it's day-to-day. I can't put a timetable on it, but the positive thing about it is it's been feeling better, showing improvement every day."
Following a victory over the Pacers on Dec. 22, Pierce returned home and started feeling pain in his knee. Within a 15-minute span, it became excruciating, forcing Pierce to phone team trainer Ed Lacerte, who went to Pierce's home to examine him.
Pierce went to the hospital Wednesday morning, but quickly realized he wouldn't be making the team's 10 a.m. flight to Orlando. Doctors performed the initial procedure, draining fluid from the knee.
While the knee felt better Thursday, it flared up again Friday, forcing Pierce to return to the hospital on Christmas night for a second procedure. Doctors didn't find an infection in a first sample taken Wednesday, but noticed a high white blood cell count. They later found the infection, but tests after Friday's procedure indicated the white blood cell count had dropped, suggesting the infection was eliminated.
"Things like this I've got to be positive," said Pierce. "I wasn't sitting there moaning because it was Christmas Day. There are people far worse off than I am on Christmas Day. I'm happy I'm still alive and, with this situation, I've just got to make the most of it. Even in the hospital I wasn't complaining."
Pierce said he is itching to get back on the court, but following the Celtics' mantra on injuries this season, he's hoping to completely recover rather than suffer a relapse later in the season.
Pierce, wearing large bandages over his entire right leg, jumped rope for the first time Saturday and got up some jumpers at the Garden. He still can't bend his knee fully and suggested that was one of the final hurdles for his recovery.
Pierce was on the bench, dressed in a brown suit and seated next to the coaching staff, on Saturday night while his teammates took on the Raptors.
"I'm always there in spirit," said Pierce. "I'll be out there today, hopefully we get a win."
Chris Forsberg is a roving reporter for ESPNBoston.com. Follow him on Twitter.