Boston Celtics president Danny Ainge said star point guard Kemba Walker was "definitely not himself" during the team's stay inside the NBA's bubble at the Walt Disney World Resort in Florida.

"I wasn't there [in the bubble]," Ainge said Thursday during his end-of-season conference call following the Celtics' loss to the Miami Heat in the Eastern Conference finals. "I was watching from here, but I could see, even when he was here before the bubble started -- which is why he was shut down a little bit and doing strength training and trying to prepare himself for the playoff run and the intensity of the playoff run -- but he was definitely not himself.

"In fairness to Kemba, he doesn't want to say that. He doesn't say that to our coaches. He doesn't say that to you, the media. He doesn't say that to me. I haven't heard one excuse from him. But watching the games, even the games we won, even the games where he played well, I could tell he wasn't the same physically as he was in October, November, December. So we're going to try to get that Kemba back."

Walker has dealt with left knee issues since January. They plagued him during the final two months before the league shut down due to the coronavirus pandemic -- especially between the All-Star Game in mid-February and when the season was halted in mid-March -- and then again after Boston returned to practice in June before heading to Orlando.

After slowly ramping up to full minutes during the six weeks preceding the playoffs, Walker looked terrific in Boston's sweep of the Philadelphia 76ers in the first round. But he appeared to tweak his left knee again in Game 1 of the Eastern Conference semifinals against the Toronto Raptors. And while he had good games after that, Walker never quite looked the same.

"I know Kemba wants to be back 100 percent and playing his best basketball," Ainge said. "Even not at his best, he still averaged 19 or 20 points per game in the playoffs. He still is a really good player, but he's not what he was. There's nothing more frustrating for an athlete to be on the biggest stage in the world in your sport and not be able to be yourself. I've been there before as a player. It's not fun. It's stressful. And Gordon [Hayward] and Kemba were trying to do that.

"I know everybody is banged up a little bit this time of year. I'm just saying those guys were ... they were limited on what they could do from what we are used to seeing in them."

Overall, Walker had a successful first season in Boston, helping to stabilize the organization after the departure of Kyrie Irving. Walker made his first deep playoff run after reaching the postseason only twice -- and losing in the first round both times -- during his eight years with the Charlotte Hornets.

"Kemba is a great person," Ainge said. "His leadership and being accountable ... he didn't make any excuses, he came to play, he realized the moment he was in. He's a player who understood how special it is to be here, and to never have those opportunities he's had in his career. But he has a smile on his face, he brings joy to the game and the team and the entire organization on a daily basis.

"He's just great to be around, and that's why I feel so bad. It's his first time on this big of a stage ... and he gave everything that he had. He played well, but we know that he wasn't himself. But he's a terrific leader and a terrific teammate and an amazing person."

This year marked the third time in four seasons that the Celtics have seen their season come to an end in the Eastern Conference finals. The first two times, Boston's losses came against LeBron James during his eight consecutive NBA Finals appearances.

This time, however, marked the first time that Boston lost to a team that was considered an underdog -- albeit a slight one. And while Ainge said he saw plenty that he liked about this season, including the growth of Jaylen Brown, Jayson Tatum and Marcus Smart, he conceded that the final outcome proved Boston was simply "not good enough."

"First of all, I've been very impressed with the development of our young players and how good they're getting," Ainge said. "Two, I think that Jaylen and Jayson are very special. Marcus played a huge, huge role for us. He's a great complementary piece for those two guys. I learned how good Kemba and Gordon are when they're healthy and how good our team is when our team is healthy.

"But I feel like there's a lot that we don't know about our team, just because the opportunities haven't come for so many of our players that are on our bench. ... I think there's a lot we learned about each of the individuals and about our team collectively. I think that we learned that we're not good enough."

One thing Ainge did think was good enough, however, was the team's chemistry, which was called into question after a locker room dustup -- one that Smart was loudly in the middle of -- following Boston's Game 2 loss to Miami.

Chemistry issues dogged Boston all of last season, when Irving and the team's young players were at odds before getting routed in the second round by the Milwaukee Bucks. This year, aside from that moment after Game 2, those issues never surfaced, and Ainge was quick to defend the way his group had come together over the course of the year.

"I would say that the entire year, I had heard nothing from our players or our coaches through Game 1 of the Eastern Conference finals," Ainge said. "I never heard anything but how positive a culture it was and what a great team we had and it was such a joy to be around, what a joy it is to watch this team play.

"I thought the same way. I really liked being around the team, I liked watching our team compete, and I liked all the guys I was communicating with."

Ainge said he didn't read too much into what happened after Game 2.

"I personally have been around a long time, as you guys can tell, and I wouldn't overreact to those [moments]," Ainge said. "I think our chemistry for sure was enhanced this year. Our team was enhanced by the great chemistry and great culture that was created here."

Entering the offseason, Ainge said Boston is prepared to pay the luxury tax -- an important point, given that, due to the pandemic and the financial havoc it has wreaked on the league, the Celtics are likely to be well into the tax next season. That will especially be true if Hayward, as expected, opts in to his $34.1 million player option for next season.

One thing that should remain constant is Tatum's presence. Despite stretches against Miami where he didn't make a big enough impact on the game, it was still a successful season as he made his first All-Star and All-NBA appearances.

Boston's title aspirations in the coming seasons will be built around Tatum and Brown, whom the team agreed with on a contract extension prior to this season.

"Jayson knows how much we like him," Ainge said. "We have a good relationship. Jayson likes it here, so I'm confident that we'll be able to work something out this summer -- this offseason, I should say."