BOSTON – Coach Doc Rivers spent the regular season trying to get his aging Boston Celtics veterans rest.

In the playoffs, the Big Thirtysomethings of Kevin Garnett, Paul Pierce and Ray Allen took care of it themselves — and 39-year-old Shaquille O’Neal, too.

The Celtics got another day off Tuesday, two days after beating the New York Knicks 101-89 to complete their first-round sweep. Boston is waiting to learn its second-round playoff opponent; the most likely opponent is the Miami Heat, who hold a 3-1 series lead over the Philadelphia 76ers heading into tonight’s Game 5.

“We haven’t swept a team in a long time,” point guard Rajon Rondo said. “It’s a good feeling to get some rest.”

The Celtics have reached the NBA finals twice in the three years since the new Big Three was assembled, winning it all in 2008. But they hadn’t swept a team since beating the Indiana Pacers in three straight in the first round of the 1992 playoffs, the last postseason series win in Larry Bird’s career.

In ’08, Boston managed to win an unprecedented 17th title after going the distance in the first two rounds, needing 26 playoff games before finishing off the Lakers in six. Last year’s return to the finals took 24 games and has been taking its toll.

Rivers thought rest was so important this season that he conceded the No. 2 seed in the East to the Heat to rest his stars in the final week rather than burn them out in a likely futile attempt to catch Miami.

“I think we do need it so we’re going to take it,” he said before sitting his starters for the last two regular-season games.

Boston has one of the oldest starting lineups in the NBA with three starters in their 30s — four if O’Neal can make it back from a right leg injury that has limited him to just 5:29 since Feb. 1. Allen is 35, Garnett turns 35 next month and Pierce is 33; they have played more than 120,000 career minutes between them.

But Pierce played fewer minutes this year than in any full season in his career. Garnett was near his career low in minutes per game. But no one could use the extra time more than O’Neal.

The former MVP and future Hall of Famer played in a career-low 39 games and 751 minutes this season, but mostly because of injury. He hasn’t played since making a cameo April 3 to return from an Achilles tendon injury. He then injured the same leg after just 51/2 minutes.

O’Neal is still listed as day-to-day, the team said Tuesday.

Jermaine O’Neal, 32, whose presence will be key if Shaq can’t play, also played his fewest minutes since becoming a full-time NBA starter in 2000.