Allen connected on 9-of-13 shots, including five 3-pointers, while pouring in a team-high 25 points over nearly 39 minutes of action. Four of those 3-pointers came in the second half as Allen tried to sneak Boston back into the game, but the ejection of Paul Pierce left Allen with a tough load to shoulder as the Celtics struggled offensively at times.
Boston shot a mere 25 percent in the first quarter (5-of-20 overall) and 35.9 percent (14 of 39) for the first half while digging a 15-point halftime hole.
"We look at the things we didn't do offensively," said Allen. "We didn't execute, or take our time, or have patience. Then it just snowballs. We had less than 40 points at the half. With the caliber of scorers we have, it's crazy for us to have only that many points [at the half]."
Kevin Garnett labored through 3-of-9 shooting with only six points, while Pierce missed eight of the 14 shots he put up before being ejected with seven minutes remaining. Boston's bench chipped in 23 points on 6-of-23 shooting (26.1 percent) and was outscored by Miami reserve James Jones (25 points) alone.
"I thought we were way too aggressive," said Celtics coach Doc Rivers. "We were too eager to score on the first pass early on. I told our guys that [the Heat were] an athletic team and you're not going to beat them with the dribble. I just thought early on we were so eager to score -- we call it 'being thirsty' -- that we never got to the second pass and we never got to the second option. I thought we were very easy to guard. We scored 90 points and we didn't have a great offensive night."
Through five postseason games, Allen is hooting a sizzling 59.7 percent (40 of 67), including 64.7 percent beyond the arc (22 of 34).
--RIVERS EXCITED AS THIBODEAU NAMED COACH OF THE YEAR--
In the hours before his team's biggest game of the season, Celtics coach Doc Rivers still took a moment to send former top assistant Tom Thibodeau a congratulatory text message after learning he had been named Coach of the Year in his rookie season with the Chicago Bulls.
Thibodeau received 76 first-place votes from a panel of 119 sportswriters and broadcasters throughout the United States and Canada, finishing with a total of 475 points to easily outdistance Philadelphia's Doug Collins (210 points, 18 first-place votes) and San Antonio's Gregg Popovich (11 first-place votes, 177 points).
Rivers lauded Thibodeau sticking with the blueprint he arrived with in Chicago.
"[Thibodeau] came in and did his job," said Rivers. "No. 1, he was so prepared for it. More importantly, I thought he followed through on what he came in to do. I think a lot of times, you come in there and you have some thoughts, but the first time there's adversity, you kind of change up and go another direction. We talk a lot, obviously, and one of the things I kept seeing was that he kept standing for his beliefs. I know when you play the Bulls, you can see his beliefs through the team. That’s always the mark of a hell of a coach."
Rivers won his only Coach of the Year award during his rookie season on the bench with the Orlando Magic in 1999-2000. When that similarity between him and Thibodeau was noted, Rivers joked, "The kiss of death." After going 41-41 in that initial season (an eight-win improvement from the previous season), the Magic combined to finish a mere six games above .500 the next three seasons and Rivers was fired after a 1-10 start to the 2003-04 campaign.
The Bulls likely won't have such a problem. A young core led by MVP candidate Derrick Rose won an NBA-best 62 games this season, a 21-game improvement after Chicago finished 41-41 last year.
--LAYUP LINE: NO CHANGES FOR WADE; RONDO'S FOULS; WEST'S TECH--
* Even after Dwyane Wade erupted for a game-high 38 points against Boston, Rivers wasn't planning to re-write Boston's defensive playbook. Asked what he'd change in Game 2, Rivers shot back, "Not a thing." Wade, who shot a mere 28 percent against Boston during the regular season, connected on 14-of-21 attempts on Sunday.
"I don't think he hit a lot of tough shots tonight," said Allen. "He scored within the confines of what they were doing. They got him in transition, he rolled to the basket, he got easy layups early and then he was getting stuff in the flow."
* Rajon Rondo labored through early foul trouble, logging a mere 8:23 in the first half after picking up three fouls.
"It was frustrating, especially when you think you can help your team," said Rondo. "[Delonte] West came in and did a great job. We made a run at it again in the second quarter, but then again, they made a run as well, so it was frustrating to get three fouls in the first half. I don't think I've had that this entire year, so to be in a playoff game, Game 1, it's just frustrating."
* West picked up a technical foul -- his second of the postseason -- in the first half for throwing the ball at Mario Chalmers. The Celtics were trying to call a timeout and West was bringing the ball over halfcourt when Chalmers tried to draw a charge near the Boston bench. With Chalmers on the ground, West threw the ball at him and the two had words.