The Celtics got an added boost on their bench for Friday’s showdown with the Hawks.

Rajon Rondo made his first appearance on the sidelines with the team since having season-ending ACL surgery on his right knee.

“It was nice. It was nice,” coach Doc Rivers said. “He told us today he was coming in, and it was good to have him back around. He’s moving okay. You know, it’s funny, I’m looking at it knowing he’s nowhere near, but that’s the first thing you look at. Having gone through that experience, we sat and talked about a lot of the stuff you have to go through. So, it brought back these horrendous memories, actually. But he’s, from his doctors, they say he’s doing tremendous.”

Rivers was asked to describe Rondo’s spirits while on the sidelines.

“Oh, I don’t know, I have no idea,” Rivers said. “I mean, I don’t care who you are, especially if you’re on a team sport I think these types of injuries are very lonely. Very hard, because rehab is all by yourself with some stranger. And you’re away from your team. Just brutal rehab. That’s what it is. He’s been in – wherever, Jacksonville, wherever, Florida, Pensacola – and that’s tough. His family has been going back and forth. But he’s made the commitment and he’s been great.”

Asked if Rondo tried to exert himself in the huddle, Rivers laughed, “No, no, no. I told him to be nice. And he was.”

The players were the most affected – and inspired – by Rondo’s presence.

“Definitely,” Paul Pierce said. “It’s good to get him around the guys, to see some of his new teammates. Who knows – a lot of these guys might be here for him next year. It’s good for him to get acquainted with them. He’s done his surgery, he seems to be in good spirits, so its good to see him.”

“It was fun. It was good to see him. He’s got a little fro now,” Jeff Green laughed. “It was good to Rondo, glad he’s doing well. Wish he were on the court but I think it was a big emotional boost for us to have him on the bench with us.”

How big of a boost was it to the players?

“It’s big,” Green said. “I think a lot of people counted us out when he went down, when Sully [Jared Sullinger] went down, too. But we’ve been coming together, doing our part, playing hard. We’ve been talking and he’s been seeing things from a different point of view.

“Definitely, most definitely,” Green added. “He sees us playing hard and that’s all you can do.”

Since Rondo had his ACL repaired on February 12, the Celtics have added several new players, including Shav Randolph, DJ Williams, Jordan Crawford (at the trade deadline) and Terrence Williams.

After the Celtics’ 100-98, double-overtime win over the Heat on Sunday afternoon, Celts coach Doc Rivers explained that he didn’t tell his players the news of Rajon Rondo‘s torn ACL injury until after the game.

“Obviously the Rondo news is pretty tough,” Rivers said. “I knew it before the game; no one else knew it. I just didn’t think it was any time to tell any of our guys that. I told them after the game. Pretty emotional in the locker room.”

Rivers said Rondo went through the team’s walk-through earlier in the day, and actually believed the injury — suffered in Friday night’s loss to Atlanta — to be a hamstring issue. But after further examination by team medical director Brian McKeon, it was determined that the point guard had torn the ACL in his right knee.

It wasn’t until halftime that Rondo was informed the extent of his injury, according to Rivers.

“Very emotional. Very emotional,” the coach said of the player’s reaction. “Funny, at halftime, I knew, and didn’t know. Still. And because Dr. McKeon knew, but he hadn’t seen the MRI. But the technician had already told him. And Dr. McKeon told me, ‘Positive, but let’s wait.’ And so that was hard, too.”

Regarding the reaction of the players after he informed them of Rondo’s injury, Rivers said, “It was good, and then it went down. … I just walked in and told them. I don’t know what else you can do. Guys were celebrating and then it just …”

The Celtics coach still relayed optimism after the game, despite there be no pure point guard on the current roster whom might step in for Rondo.

“Well, you can write the obituary. I’m not,” Rivers said. “You can go ahead. But I’m not. We won tonight, and so the way I look at it is: we’re going to stay in there. In my opinion, we’re going nowhere.”

To hear Rivers’ entire postgame press conference, click here.

For more Celtics news, go to the team page at weei.com/celtics.

Rajon Rondo is done for the season with a torn ACL. (AP)

Rajon Rondo is out for the season after suffering a torn right ACL, the Celtics confirmed in the third quarter of Sunday’s game with the Heat.

After getting a MRI at New England Baptist Hospital, the diagnosis was confirmed by team doctor Brian McKeon.

The Celtics said the star point guard would have surgery to repair the injury at an unspecified date.

Rondo returned to TD Garden in the third quarter in the warmups he was wearing when he left during pregame warmups, walking with a slight limp but no crutches. He walked down to the Celtics locker room on his own power.

Rondo came to the Garden Sunday morning for his normal pregame shootaround but went back in for more treatment on the knee as the pain continued in his right knee. He was taken to the hospital with a preliminary diagnosis of a hyperextended knee.

Courtney Lee started Sunday’s game in Rondo’s place. For more, visit the Celtics team page at weei.com/celtics.