The Heat, though, knew it would take time to jell.
"This is one of 82," Wade said. "Sorry if everyone thought we were going to go 82 and 0. It just ain't happening."
Celtics coach Doc Rivers is convinced the Heat will progress into a championship contender.
"They're going to be great," he said.
Not yet, though. Wade and Bosh weren't even all that good on opening night.
Wade was limited to 13 points on 4-of-16 shooting and Bosh added eight points and eight rebounds. The trio combined for 15 of the Heat's 17 turnovers -- eight by James, six by Wade and one by Bosh.
"Right now it's a feel-out process for myself, for D-Wade, for Chris and for the rest of the guys," James said.
James announced his intention to leave Cleveland for Miami, revealing "The Decision" on national television 110 days before the opener.
Tuesday's decision went to the Celtics behind 20 points from Ray Allen, 19 from Paul Pierce and 10 points and 10 rebounds from Kevin Garnett. Shaquille O'Neal, James' teammate last season, had nine points and seven rebounds for Boston. The Big Shamroq was just another reason for all the excitement surrounding the game.
"I just said to Paul as we were coming in here," Garnett said after taking his seat at the postgame news conference. "I said, `Are we in the finals already?' You know, but it did have a lot of hype on it."
Boston led 45-30 at halftime, but Miami cut that to 63-57 after the third quarter behind James' 15 points in that period. A layup by James made it 83-80 with 1:10 left in the game. But Boston, which once led by 19, got the last five points on a 3-pointer by Allen and two free throws by Pierce.
Boston led 16-9 after one quarter, the first time since March 15, 2009, at the Philadelphia 76ers that the Heat scored nine points or fewer in a period. The last time James' Cavaliers scored nine or fewer points in a quarter was February 2, 2007, when they managed nine in the second against the Chicago Bulls.
Things got so bad for the Heat in the first half that O'Neal, a notoriously poor free throw shooter, made the first two he tried as a Celtic. That boosted the lead to 41-22 with 2:13 left in the second quarter.
Miami then got a brief burst, scoring six straight points to make it 41-28. The last basket in that surge was a dunk by James on a backward pass from Eddie House, whose steal started their 2-on-none break.
That drew cheers from two Heat fans -- one wearing a T-shirt with James' name on the back and the other with a jersey bearing Wade's name -- but a fan wearing a green Celtics T-shirt, yelled, "He's supposed to do that. That is not impressive."
It was pretty impressive, considering how poorly the Heat shot in the first half against a quick, aggressive Celtics defense.
Miami missed 30 of its 41 shots, a paltry 26.8 percent. Boston went 17 for 38 (44.7 percent).
The Celtics lost Pierce with 4:32 left in the third period when he hit the floor and hurt his back as he was charged with a blocking foul on James, who made two shots and cut the lead to 55-45. Pierce returned with 10:43 left in the game with Boston ahead 64-57.
James came back to the building where he lost the last game of his Cleveland career in Game 6 of the Eastern Conference semifinals. He then became a free agent after seven seasons with the Cavaliers and signed with the Heat.
Notes: James' 31 points were the most by a Heat player in his debut, passing the 25 scored by Antoine Walker and Willie Burton. ... Among the Boston athletes watching from the stands were David Ortiz of the Red Sox and Wes Welker, Vince Wilfork, Deion Branch and Brandon Meriweather of the Patriots.