Is your team leading the Miami Heat at halftime? Don't get too comfortable

Entering halftime of Game 1 of their Eastern Conference finals matchup with the Miami Heat on Wednesday, the Boston Celtics appeared to be in good shape. Not only were they leading by nine on their home floor, but they’d forced nine Heat turnovers while hitting nearly 55% of their own shots. They were dominating the action on both ends of the court and appeared poised to cruise to an easy victory.

Then, halftime arrived. And everything changed. 

The Heat caught fire from deep. They ceased coughing up the ball. In the third quarter, they went on a 17-3 run and outscored the Celtics 45-25. 

"[We] lost our game plan discipline," Boston head coach Joe Mazzulla told reporters Wednesday night following the Heat’s stunning 123-116 win, their third time taking Game 1 on the road this postseason. "Allowed them to get out in transition, get second-chance shots, didn’t guard the 3-point line."

It won’t make Mazzulla feel any better, but he can take solace in knowing that his Celtics aren’t the first team the Heat have dominated in the second half of a playoff game. In fact, the ability to adjust during the break and pummel opponents in the second half might be one of the best ways to quantify the vaunted #HeatCulture, illustrate Erik Spoelstra’s brilliance as a coach, and explain how the Heat —  a no. 8 seed that was outscored by opponents in the regular season — keep defying expectations.  

This postseason, the Heat have outscored opponents by 10.5 points per 100 possessions after halftime. Last year, while taking the Celtics to seven games in the conference finals, they outscored opponents in the second half of games by 7.3 points per 100 possessions. Two seasons earlier, during their run to the Finals in the bubble, that mark was 7.4.

After Game 1, Heat center Bam Adebayo was asked what changed at halftime. 

"We have a great video group, and they put up all the stats at half," he said. "[They] basically showed us where we were wrong and how we can improve in the second half." 

That list was long. The Heat had surrendered 40 points in the paint. The Celtics had torched their zone defense. Celtics star Jayson Tatum was too comfortable (18 points). The Heat weren’t taking care of the ball. Also — and most troubling — their energy was lacking. 

But it’s one thing to identify the issues. The real skill — one which Spoelstra clearly has — is being able to communicate them to a team during a game’s 15-minute halftime window while laying out a plan of how it can be fixed. 

For the Heat, this means leaning on the collaborative environment fostered by Spoelstra. 

"After watching [the film] and talking to the coaches," Adebayo said Wednesday night, "we are honest with one another, look each other in the eye and say how we feel and what we need to get done."

What was jarring about their dominant second half in Game 1 is just how many adjustments the Heat were able to make. It wasn’t just that their jumpers started falling. They upped their energy level (they rebounded four of their own nine misses in the third quarter), and stopped tossing the ball all over the court (just three turnovers in the second half, compared to 10 in the first). They kept the ball out of Tatum’s hands (he didn’t attempt a single shot in the fourth quarter) and kept the Celtics out of the paint (just 22 points surrendered in that area). They took the Celtics out of their game by slowing the pace. 

Just look at how Tatum described what happened to his team during the third quarter. 

"We gave up some transition baskets, they got in a rhythm, they were comfortable," he said. "We didn't close out to shooters. We gave up some offensive rebounds."

Of course, this being the Heat, their own player had a more succinct way of summarizing their second-half performance. 

"It’s just a mentality," Heat guard Gabe Vincent said. "Sometimes you have to get punched in the mouth to wake up a little bit."

Yaron Weitzman is an NBA writer for FOX Sports and the author of Tanking to the Top: The Philadelphia 76ers and the Most Audacious Process in the History of Professional Sports. Follow him on Twitter @YaronWeitzman.