Doc Rivers wants everyone to take a deep breath before Sunday’s latest and greatest ‘Most Important Game of the Year’ against LeBron James and the Cleveland Cavaliers.

“I think we’ll come in and play terrific,” Rivers said. “But we just have to play hard. There’s no guarantees. But listen, it’s a big game for them, too. It ain’t just one way. I always laugh when I hear guys say it’s a must win. But what if it’s a must-win for both teams? Someone’s not going to win.”

The Celtics (41-23) are coming off a 19-point win over Indiana on Friday night at home and trail third-place Atlanta by a half-game in the East. Meanwhile the Cavs come in with a 51-15 record, and lead the Lakers by three games for the best mark in the NBA.

LeBron James is playing his second game back from a sprained right ankle.

“It would be great, though,” Rivers said of a win in Cleveland. “I think our team is looking forward to it,” Rivers said. “And I guarantee you they’re looking forward to it. There’s no coincidence that LeBron James rested two games and came back. That’s not a coincidence but that’s fine.”

The Cavs will be without Shaquille O’Neal, likely out for the rest of the regular season following surgery on his right thumb, injured the last time the two teams met when Glen Davis went up to block an O’Neal shot. On Sunday, Davis denied hurting O’Neal intentionally during their Feb. 25 meeting.

“They’re playing the same guys, really. They haven’t changed their offense or anything. They’re quicker, faster, more athletic.”

The Celtics are visiting Cleveland for the first time since Oct. 27, when they claimed a 96-89 win over the Cavs on opening night.