That's why it had to be deflating when LeBron James, strained right elbow and bone bruise be damned, cruised to the basket on the Cavaliers' final possession of the third quarter and nailed a running layup, giving the Cavs their first lead of the second half at 79-78.
From there, it was all over. The Cavaliers tore the Celtics apart in the fourth quarter, driving past them on offense and stifling their every opportunity on D, waltzing to a 101-93 victory in Game 1 of the Eastern Conference semifinals.
For those final 12 minutes, the Celtics just never seemed in it.
It's a shame, considering how thoroughly they dominated the first 36.
"We did a good job of getting out to a lead," said Rajon Rondo, who contributed 27 points, 12 assists and six rebounds in the losing effort. "We had them by double digits going into halftime. I mean, what more can you ask for in a road Game 1? But then they came out swinging, and I think we just shied away from doing what were doing, being aggressive."
Things starting unraveling in the third, when Mo Williams went off for 10 consecutive Cleveland points in the third quarter, eating away at the late Boston lead.
The Cavs sent a message in that second half. Not in our building, they said. If you want to win Game 1 at our place, you've got to do better than that.
"We were playing a pretty good team," Boston coach Doc Rivers said. "You knew they had a run in them. It happens. I didn't think we absorbed the run very well. They were going to make a run. You thought it would be LeBron doing it more than Mo Williams, but it was Mo Williams. I thought that stretch changed the game."
The tail end of Williams' run, a pair of free throws with 3:12 left in the third quarter, cut it to 73-68 Boston. Then the Cavs' bigs got involved — Antawn Jamison, Anderson Varejao, J.J. Hickson. Then LeBron beat the buzzer and put the Cavs in front.
The Celtics just didn't have the steam to fight back.
The fourth quarter wasn't a war — it was a surrender. They got their lead on the strength of Rondo's driving and scoring, and his distribution to open teammates. But when the game got close and the pressure built, the game plan crumbled. They lost at one-on-five basketball, trying to knock down tough shots rather than win as a team.
"I thought in the third and fourth quarter, we decided to settle with our jump shots," Rivers said. "Very rarely did we go down low and play in-and-out basketball anymore. You know, [Cleveland's] pressure had a little bit to do with it, so give them credit. But I just thought we went away from our game plan, and we needed to sustain 48 minutes of focus."
The Celtics as a team shot 5-of-19 in fourth quarter. They made it rain with missed 3-pointers — first Paul Pierce, then Ray Allen, then Allen again, then Pierce again. Time and time again, they had chances to make clutch plays but came up empty.
They were playing like a team defeated. Talk about a self-fulfilling prophecy.
There's still a long way to go in this series. But it's worth bearing in mind that the Cavaliers are 8-0 in postseason series after winning Game 1.
You let LeBron land that first punch, and the knockout becomes inevitable.
For 36 minutes, the Celtics stood their ground. But in the last 12, it all came tumbling down. They should have known better than to give the Cavs an opening.
