The Miami Heat were tabbed as the team to compete with the Cleveland Cavaliers in the Eastern Conference back in October, entering this season with a loaded roster of Dwyane Wade, Chris Bosh, a rejuvenated Goran Dragic, Luol Deng, and prized rookie Justise Winslow.

Winslow was the Duke kid the Celtics offered at least four draft picks to Charlotte to move up to draft. Instead, the Heat took him 10th. They were ready to roll after a tough post-LeBron James transition season.

Nothing has gone as expected for Miami. Bosh is out with another potentially scary blot clot issue, the same condition that cost him most of last season. Much of the rest of roster has dealt with various injuries. Still, the Heat entered Saturday just a game behind the Celtics for the third seed in the East.

The Celtics blitzed the Heat in the fourth quarter, scoring 29 points en route to a 101-89 win in what was a mistake-filled, defensive battle where neither team shot 42 percent.

In the Miami locker room, the players awaited much-needed relief. Just about an hour after the game, former Brooklyn Net Joe Johnson officially committed to Miami after clearing waivers. He will immediately start at small forward, taking the minutes of the struggling Gerald Green, who did not score in 19 minutes Saturday.

The Heat need a boost. Bosh’s status for the rest of the season is uncertain, and players aren’t expecting a rapid return considering his past. The Heat were built to compete now, while Wade still has a sliver of his prime left. Wade, who has only missed five games despite it being his 13th season, has been sturdy while everyone around him has experienced issues.

Hassan Whiteside was marvelous defensively when engaged Saturday with 13 points, 15 rebounds, and 8 blocked shots in just under 33 minutes. His minus-17 seemed mystifying, but further investigation found that Whiteside didn’t always get back on defense, allowing for easy layups or attempts at the rim.

Wade had a bizarre performance of 19 points on 19 shots and four turnovers. He is always bothered by the smothering defense of Avery Bradley, and when the Heat needed “Flash’’ to appear down the stretch, Wade didn’t appear to have the energy, settling for mid-range jump shots.

He sat shirtless in the Miami locker room, compression sleeves around each leg, explaining his pleas to attract Johnson to Miami when he could have easily chosen Cleveland or Toronto.

“To put somebody on the floor who can shoot the ball, can score in different areas on the floor, make plays just adds to what we’re trying to do,’’ Wade said. “Another playmaker, another scorer in games like this is when you’re missing your All-Star [Bosh]. Joe’s a friend of mine. I tried to do my best job to paint the picture that’s it’s a good place to be. I made sure my name was in his inbox a lot. We’ll welcome him with open arms in Miami.’’

This NBA buyout season can be beneficial for some teams, especially in locations like Miami. Johnson appeared sold on the immediate opportunity to start and fill a much-needed scoring role for a team that entered Saturday 28th in the NBA in scoring.

Coach Erik Spoelstra has been plugging holes with stopgaps, such as aging Amar’e Stoudemire at center. Stoudemire looked like the Stoudemire of old with 6 points in eight first-quarter minutes but didn’t score again. Green brought little to the game when his shot wasn’t falling. Though Winslow (6 points) was an early factor, he isn’t quite yet ready to fill a major scoring role.

The Heat hope they are a different team when they come to TD Garden in April for the regular-season finale. Johnson still has something left, and his offensive production really increased the past two months after a poor November and December for the Nets.

Miami is banking that Johnson will be rejuvenated in his tenure in South Beach, while Bosh will be able to return.

The Celtics are a team that has stayed mostly healthy this season and coach Brad Stevens has been able to depend on his bench for quality minutes, such as Saturday when the reserves nearly outscored the starters (52-49) and did outscore their Miami counterparts (49-26).

Stability has been one of the Celtics’ biggest strengths all season and their depth offered support on a day when Isaiah Thomas scored just 12 points on 4-for-17 shooting and Bradley managed just 9 points. The Heat don’t have those luxuries, even though president Pat Riley thought he adequately prepared for that in the offseason.

Johnson would have come off the bench for the Celtics. His role would have been undetermined. In Miami, he is desperately needed. So the Celtics can be grateful for their health and depth. Depth is what beat the Miami Heat on Saturday and stability is what should carry them to home-court advantage in the first round of the playoffs.

Miami expects to be a different team when it returns to Boston on April 13. The Heat will have to be if they plan to compete with Cleveland, Toronto, and others in the Eastern Conference. They simply ran out of fuel­ Saturday.

Gary Washburn can be reached at gwashburn@globe.com. Follow him on Twitter @GwashburnGlobe.