After Udonis Haslem clobbered him in the head during Game 3, Kevin Garnett, center, dropped and did eight push-ups on his knuckles. (Charles Krupa/Associated Press)

For so long, Kevin Garnett has been in denial. Not only did he not want to play big, he didn’t even want to be big. Throughout his career, he has demanded to be listed at 6 feet 11 because it sounded cooler, even though he is at least an inch or two taller. He’d probably accept a listing of 6 feet 13 before allowing himself to join the ranks of other 7-foot giants.

Garnett also has often preferred to avoid the grittier parts of the paint, eschewing overly physical play with a game that is about more bark and bluster, chest thumps and basket-stanchion head butts. He could always ease out of the painted area and rely on a buttery-smooth jumper to carry him, shooting over the top of most defenders and occasionally ducking inside for dunks.

As he gets older, Garnett can still give his team consistent production from the perimeter. But with the Boston Celtics forced to play what he called “desperation basketball” in Friday night’s Game 3 of the Eastern Conference finals against the Miami Heat, Garnett finally decided to take advantage of his height and take ownership of the semicircle around the rim in leading his team to a much-needed victory.

He absorbed elbows, shoves and hard fouls and came back for more, showing his cantankerous nature when Udonis Haslem clobbered him in the head and dropped and did eight push-ups — on his knuckles.

“He played great,” Heat Coach Erik Spoelstra said of Garnett. “He was able to get into a real good comfort zone.”

With all-star forward Chris Bosh sidelined the past seven games with a strained abdomen, the Heat has been forced to defend Garnett with three players who are 6-10 or shorter in Ronny Turiaf, Joel Anthony and Haslem. LeBron James and Mike Miller even took turns. Miami has employed a strategy of fronting Garnett in the post. The Celtics countered with Garnett rolling to the basket and letting his teammates, mostly the cerebral Rajon Rondo, find the right angles for lobs.

“One of the things we kept telling them at the end of the day, throw it up. There’s nobody taller than him on the floor,” Celtics Coach Doc Rivers said. “Throw it up in the air, Kevin will go get it.”

Garnett had a team-high 24 points in Boston’s 101-91 victory — with 20 coming on shots at the rim or from the foul line — and was largely responsible for the Celtics getting a playoff-high 58 points in the paint against Miami.

Garnett is averaging 19.7 points this postseason, his best scoring average in the playoffs since the Celtics claimed Banner No. 17 in 2007-08, his first season in Boston. He is also shooting 50.4 percent from the floor — the second-best of his playoff career — and that efficiency can be attributed to a greater willingness to attack the middle.

“I mean it’s interesting, because Kevin is a jump shooter,” Celtics guard Ray Allen said, “but he’s had such great matchups.”

Before having his way in Game 3, Garnett did a lot of the heavy lifting against the undersize Atlanta Hawks and Philadelphia 76ers.

Garnett has only been around for four of the five postseason runs in Boston, with a knee injury sidelining him in 2009, but Rivers said the team probably hasn’t seen him more aggressive or assertive.

“Yeah, but we’ve had to be. In these series that we’ve had, he’s had an advantage post-wise in all three and so we have to try to take advantage of it,” he said.

At 36, Garnett has been rejuvenated since making the reluctant yet rewarding move to center, which has spared him from chasing younger and more athletic power forwards and allowed him to be more dominant. The switch has done more than give him more bounce; it has made the Celtics better as they have reached the conference finals for the third time since he and Allen joined Paul Pierce and Rondo.

Garnett will be a free agent after this season, raising speculation that this second act has been motivated by another big contract push.

But he doesn’t know how many more legitimate chances he’ll have to win a championship, especially in Boston, where the Big Three era with him, Pierce and Allen will likely close once this season ends.

“We have to get these two at home, by any means necessary and deal with whatever happens after that,” Garnett said. “I feel like the way we played Game 3 is the way we have to play. This team [Miami] is too athletic, too good, too confident, too well-coached, too sound defensively to come in here any other kind of way.”