BOSTON — On Dec. 18, the rebuilding Boston Celtics traded off point guard Rajon Rando.

On Jan. 12, the club dealt leading scorer Jeff Green.

On Feb. 11, forward Jared Sullinger was supposed to be lost for the season with a broken left foot.

On Sunday, the Celtics moved closer to grabbing a playoff spot, trouncing the undermanned Cleveland Cavaliers 117-78 on Sunday.

Sullinger even came back early to help the late run.

The win, Boston’s third in a row and 18th in the last 27 games, left the Celtics in seventh place in the Eastern Conference and reduced their magic number for clinching a playoff berth to one — pending the outcome of the Pacers’ home game against Oklahoma City later in the day — with two games remaining. They lead the eighth-place Brooklyn Nets by a game and also own the tie-breaker.

“All year we’ve been talking about focus on what’s next. And what’s next is Toronto (Tuesday night, at home),” said Celtics coach Brad Stevens. “And yes, we are one game away, but winning a game in the NBA is awfully difficult.”

Asked what happens if the team clinches Sunday night, the coach said, “Toronto walk-through at 11 a.m. on Tuesday … nothing changes at all.”

The Cavaliers, who will be the No. 2 seed in the Eastern Conference (and would play Boston if the Celtics are seventh), played without LeBron James, Kyrie Irving, Kevin Love and J.R. Smith. James and Smith were on the bench while the other two were getting treatment and Cleveland offered resistance at the start. But the Celtics (38-42) ran to a 34-9 second quarter lead and that was that.

Guard Isaiah Thomas came off the bench and led seven Celtics in double figures with 17 points, adding six assists. Guard Evan Turner had 15 points, seven rebounds and five assists and forward Kelly Olynyk had 10 points and seven rebounds and Sullinger had 11 points and four assist off the bench.

“It’s everything,” Thomas said of making the playoffs. “In my NBA career, I haven’t been to the playoffs, so it’s something that I want to experience. I heard it’s fun, it’s exciting and it’s a new season.

“Once you make the playoffs, everybody’s 0-0 and it’s a new season so I’m excited about it. Hopefully we do get it.”

Cavaliers turned the ball over 25 times in the game while the Celtics had an NBA season-high 20 steals, one shy of the club record. They reached double figures in steals in four straight games for the first time since 2005. Cleveland had one steal and the Celtics committed just nine turnovers.

The Celtics built their lead to 32 points in the final minute of the third quarter.

“It’s almost not a fair situation to put them in because most of these guys are used to playing with the other guys and feeding off of them and then suddenly they’re in primary roles,” said Cavs coach Dave Blatt.

Guard Iman Shumpert led the Cavaliers with 15 points, 10 rebounds and three assists. Center Timofey Mozgov, the only starter playing in the game, had nine points and eight rebounds.

By losing, the Cavaliers put themselves in position to play the Celtics in the upcoming playoffs, which may well be preferential to meeting the Nets or Pacers.

Asked if an Indiana could be upset at the players sitting out, Blatt said, “Indiana wasn’t upset when they played us and we had to sit a player or two. That happened in the middle of the season — we played Indiana in Indiana and we sat LeBron because it was tough back to back after plane failure and we flew in the day of the game. That didn’t bother them then. I don’t see what would bother them now.