If the Celtics are to fulfill their quest for a second consecutive NBA championship, it appears they will have to go the distance without star forward and emotional leader Kevin Garnett.
"Yes, he's out," Rivers told the Globe. "I feel for the season, but we just don't know yet."
Rivers also said Garnett will likely have offseason surgery on his right knee to remove a bone spur. But a strained popliteus tendon -- and not the spur -- has affected Garnett's inability to return, Rivers said. The tendon strain must heal naturally, and has taken longer than anticipated.
A team spokesman confirmed that the team is approaching the postseason as if the 12-time All-Star and reigning Defensive Player of the Year will not be able to participate. In his second season with the Celtics, he averaged 15.8 and 8.5 rebounds per game.
“I’m devastated for him,” Celtics guard Ray Allen said at practice. “This is the time of year you’ve been waiting for.”
The decision was made after Garnett, who has missed the last nine games and 22 of 26 overall since injuring the knee, struggled during an early workout this morning.
"After today, there's no way he can play," Rivers said during an interview after Garnett's workout on sports radio WEEI this morning.
An NBA source confirmed to the Globe that Garnett was only about 70 percent healed from the knee injury. Surgery is now being considered, but there is no timetable.
"This is the first time I've said it, because it's the first time I've really watched him," Rivers told WEEI. "He's not gonna be ready. After watching him run, there's no way. So, we're gonna move without him. And the way I saw him move today guys, I don't know if he'll be ready . . . he's just limping. He just can't run . . .
"This was an honest run today, you couldn't fake your way through it . . . and the guy is a warrior, you can see him trying to mask it, but after 20 minutes of running, there's just no way. I don't see it. I just don't. And I've flipped completely because I was watching him move, and he looked great, and then . . . after today, there's no way he can play.
"If he can't get through biking and working out without swelling and stiffness and his leg locking, I just don't know how you play in the playoffs."
Rivers added that Garnett would continue to get treatment in the slim hopes that he would be able to return at some point, but emphasized again that it's a very long shot. As one might expect, the intensely competitive Garnett did not take the decision well.
'He was frustrated. He was mad at me, mad at everybody. Then he understood," Rivers said. "He put up a fight. He's really frustrated, but that's Kevin. That's why we got him, because he cares so much."
Despite the discouraging news, Rivers was positive about the team moving forward: "I think we're going to be fine . . . we have some mentally strong guys, very tough guys."
Garnett was at the team’s practice facility this afternoon but did not want to talk to reporters, Rivers said.
Though Garnett did not appear at games while he was recuperating in the regular season, he is expected to travel with the team and sit on the bench.
“He’s the unquestioned leader of the ballclub. He can help us just by being on the bench,” Paul Pierce said. “The type of competitiveness that he has, I’m sure it’s eating at him.”
Garnett chooses to watch games from the locker room rather than the bench when he is injured because it frustrates him to not be able to contribute. But owner Wyc Grousbeck said during an interview with WEEI this afternoon that the Celtics want him to change his policy during the postseason.
"I think that's essential, and I think we're going to ask him to do that," Grousbeck said. "I think Doc, Danny [Ainge], everybody will make it clear that we'd like his presence out there. He is a warrior in every way. I mean, unusual sounds strong, but he is the most different guy any of us has ever met over here. He just does it in his way, and it works, and he became Defensive Player of the Year, MVP formerly, and now a champion. It's Kevin Garnett, it's not anybody else. There's never been another one like him.
"If he needs to sit in the locker room just to be able to keep his head together, we can respect that. And it actually worked pretty well for us in the regular season. But I think, playoff-time, we'd like to have him out on the bench."
Grousbeck admitted that Garnett's situation only secures top-seeded Cleveland's position as the favorite in the Eastern Conference.
"They earned home court, they earned the best record, they are clearly a championship-quality team, and in my opinion they have the best basketball player on the planet right now . . . Mo Williams," Grousbeck said, his sense of humor apparently intact. "They are the favorites, and there's a reason they're the favorites, and we're going to have to do something really heroic to get them. I respect Cleveland, and wouldn't be surprised if they won the whole thing. But I'm going to do everything I can to prevent it."
It's an attitude shared by the Celtics' coach, despite today's disappointing news.
"We'll be ready, I can guarantee you that," Rivers said.
The Globe's Frank Dell'Apa, Chad Finn, and David Lefort contributed to this report. Material from the Associated Press also was used.