Not long before the Celtics raised Paul Pierce's No. 34 to the rafters Sunday, one of Pierce's longtime rivals -- LeBron James -- was in the building for a matinee between Boston and Cleveland.

Pierce and James had many memorable playoff battles, including Pierce going on to win the NBA Finals after scoring 41 points in Game 7 of the 2008 Eastern Conference Semifinals to eliminate the Cavaliers despite 45 points from James.

But James had the last laugh this time around.

James stole Pierce's spotlight with 24 points, 10 assists and eight rebounds to power the Cavaliers to a statement 121-99 victory against former teammate Kyrie Irving and the Celtics in a battle of Eastern Conference heavyweights at TD Garden.

Cleveland was playing its first game with a full squad after making a series of deadline-day trades to retool its roster, with George Hill, Rodney Hood, Jordan Clarkson and Larry Nance Jr. all making their Cavs debuts.

Clarkson finished with 17 points while Hood and J.R. Smith each added 15. Hill had 12 and Nance chipped in five to help the Cavs to a second straight win.

Irving led the Celtics with 18 points and five assists. Marcus Morris was the only other player in double figures with 17 for Boston, which dropped its second straight.

James' fadeaway with 8:07 remaining in the first half tied things at 40 after Boston led for much of the first quarter.

Cleveland proceeded to close out the quarter on a 24-12 run to go up 64-52 at halftime and outscored the hosts 31-22 in the third.

The Cavs led by as many as 29 in the fourth.

James gave Cavs fans a scare when he left the game after suffering an apparent right leg injury late in the first quarter. He barreled into Boston's Aron Baynes driving to the basket and was called for the charge before limping to the sidelines.

After being treated on the Cavs' bench, James checked back into the game with 8:58 left before the break.

Following the game, the Celtics held a ceremony to retire Pierce's number. The 10-time NBA All-Star played 15 seasons in Boston, winning the one Finals series and playing in another in 2010.

Cleveland caps a three-game road trip Tuesday in Oklahoma City. Boston will try to regroup Wednesday night against the Los Angeles Clippers.

--Field Level Media