CLEVELAND — The elbow's fine.

Hours before receiving his second straight MVP award, LeBron James scored 35 points and Mo Williams added 20 as the Cleveland Cavaliers, outplayed for most of the game, stormed back to beat the Boston Celtics 101-93 on Saturday night in Game 1 of their Eastern Conference semifinal series.

James, playing with a sprained and bruised right elbow, delivered yet another memorable performance as the Cavs withstood a furious punch from the Celtics, who led by 11 in the third and seem intent on making this a long series.

James, who also had seven rebounds and seven assists, drained a 3-pointer with 22 seconds left to put Boston away.

Rajon Rondo had 27 points and 12 assists and Kevin Garnett finished with 18 points and 10 rebounds for the Celtics, who were held to 15 points in the fourth quarter.

Game 2 is Monday night.

For three quarters, the Celtics looked like their old selves.

Dismissed as being washed up, the 17-time NBA champions controlled the tempo from the start. With Rondo driving past Williams and any other defender in front of him, the Celtics were on the verge of swiping home-court advantage away from Cleveland.

But James, who seemed to be bothered by the elbow early on, picked it up down the stretch.

He always does.

After Rondo split a pair of free throws with 4:30 left, James drove the lane and missed a short shot but grabbed his own rebound and scored to put the Cavs ahead 94-91.

Garnett's bucket got the Celtics within one, but James countered with a floater in the lane. After Paul Pierce missed a wide-open 3-pointer, Shaquille O'Neal, who looked slow and old during stretches, scored on a tip to make it 98-93 with 1:02 remaining.

Following a Boston turnover, James came up with the decisive blow. Pulling up on the left side, he buried a 3-pointer that finally allowed 20,000 Cleveland fans to exhale and scream their lungs out. He finished with 12 points in the fourth.

James tried just two outside shots in the first half, and came out of the locker room at halftime shaking his right arm, which he said has been bothering him periodically for a month. But it appeared perfectly fine when James needed it to be.

"Throughout the game it loosened up," said James, who will receive his MVP trophy on Sunday in Akron. "I have a no-excuse policy. This team has a no-excuse policy. ... We're about coming out and competing against the Celtics."

James closed the third with a twisting, falling-down layup at the horn, capping a 21-9 spurt that put the Cavaliers up 79-78, their first lead since 7-6.

Williams, though, was the one who carried the Cavs back. He scored 14 in the period and delivered his first unofficial dunk in the NBA, a facial on Pierce that ignited the Cavs and a sellout crowd that was growing nervous with every Rondo drive, Garnett bucket and Ray Allen jumper.

Cleveland trailed 69-58 when Williams grabbed a loose ball and raced down the floor before slamming it over Pierce, who was probably expecting the guard to try a layup.

"I saw Paul and I had to make an executive decision," Williams said.

This is the second time in three years that the Cavs and Celtics are meeting in the conference semifinals. In 2008, the Celtics won a rugged series in seven games on their way to a championship.

As they plodded through the regular season, the Celtics were labeled past their prime, a team whose window for winning another championship was closed.

Too old.

"The old is true," Celtics coach Doc Rivers joked before the game. "We are old. And we're not going to hide from that at all. We're very old. We're just going to bring our canes out and see what we can do with them."

The Celtics were the better team in the first half. Their ball movement was crisp and the Cavs had no answer for Rondo, who had 19 points before the break.

Cleveland put the 6-foot-6 Anthony Parker on Rondo in the third quarter and the adjustment slowed the Celtics' point guard.

James was never convinced Boston wasn't dangerous, and his suspicions were proven correct when the Celtics hardly looked like Relics in the first round, dismantling the Miami Heat in five games.

"Everyone was saying how bad Boston was and they don't look motivated anymore, but I never fell into that trap," James said. "I could tell that that team was ready for a challenge and ready for the playoffs to start. You could see it against Miami, they were ready for a new challenge. Just like San Antonio, these aren't teams that are about the regular season as much as the big picture. They know the big picture."

The Celtics came out attacking, opening a 10-point lead early in the second quarter.

NOTES: Celtics C Kendrick Perkins had his lip split open by O'Neal in the first quarter. He got five stitches and was back on the floor for the start of the second. ... Recording star Usher, one of the Cavaliers' minority owners, sat courtside. ... Celtics G Tony Allen was slapped with a technical in the second quarter for complaining from his seat on the bench. ... Rivers was asked if either team would reach 100 points in any game. "Eventually, when you add the three or four games together," he cracked. "It'll happen. Someone will do it and hopefully it'll be us. Both teams are great defensively, but both teams are pretty efficient offensively when you look at field goal percentages."

AP-WS-05-01-10 2316EDT