Disappointed with his performance in Miami's loss Saturday at New Jersey, O'Neal scored 21 points to help lead the Heat to a 114-98 victory over the Celtics on Monday night.
"I had to apologize to the coach and the team," O'Neal said of his 11-point outing against the Nets. "It was a terrible performance by me."
O'Neal also finished with six rebounds and two blocked shots and his three-point play increased Miami's lead to 99-80 with 5:53 remaining in the game.
"Throughout my career, I've never had two [consecutive] games like that. I had to come back with more energy."
Dwyane Wade scored a game-high 34 points and also had eight rebounds and eight assists. He also scored 11 points in the Heat's 22-6 run that put the game out of reach.
"It was an NBA win; good teams of course are going to get the lead, but some teams are going to come back and make a run," Wade said. "You just have to withstand their run."
The Heat held a 77-74 lead with a 1:13 left in the third quarter, before going on their decisive run over the next seven minutes to seal the victory.
"I thought we played better as far as moving the ball," Heat coach Pat Riley said. "The one thing that happened the other day in New Jersey and where we get into problems is that we have a bunch of guys that love to attack, and sometimes when we attack too much we don't get off the ball."
"We've got to keep our heads up; we're going to turn this thing around sooner or later," Pierce said.
Wade's field goal 1:40 into the third quarter gave the Heat a 61-46 lead before the Celtics went on an 8-0 run. Raef LaFrentz keyed the run with a 3-pointer and a field goal that helped cut Miami's advantage to 61-54 with 8:50 left in the third quarter.
Pierce's two free throws with 1:45 left in the third cut Miami's lead to 77-74. But the Heat started their game-clinching run with Wade hitting six free throws to end the quarter and give the Heat a 83-74 edge.
"Some nights we have guys trying to do too much; we're trying to find our groove," LaFrentz said.
Celtics coach Doc Rivers said his reserves could not keep the team within striking distance after the starters made their run in the third quarter.
"Tonight, when [the first unit] went out at the end of the [third] period, it was a three-point game, and when they came back in, we were down 15," Rivers said. "You feel for the starters because they work so hard to get us back in games, and then our bench gives it up.
"It's frustrating for all of us."
The Heat's reserves outscored the Celtics' backups 30-18. Former Celtic Antoine Walker led the Heat's second unit with 12 points, all in the fourth quarter. Two of Walker's points came on a rare dunk.
"It was only about my third dunk of the season, so I had to enjoy it," Walker said.
Miami erased a 20-19 Boston lead with a 13-6 run in the final 4:49 of the first quarter.
Wade's dunk 2:13 into the second quarter increased the Heat's lead to 37-28. Brian Scalabrine's tip-in of Pierce's missed shot cut Boston's deficit to 41-36 with 4:49 remaining in the second quarter.
But Wade scored six points and James Posey hit a 3-pointer as the Heat finished the half on a 12-5 spurt and held a 55-41 advantage.
Wade has scored 20 or more points in 11 consecutive games, one shy from a career and franchise high he shares with Alonzo Mourning. ... LaFrentz started his 400th career game. ... Boston's Al Jefferson missed his second straight game with a right ankle sprain.