“They got everything they wanted, and more, in the first half,’’ LeBron James said.

If the Heat were to beat the Celtics at home, they would need to up the effort, to improve the defensive intensity.

When they came out after the break, that was exactly what they did. After allowing 61 points to the Celtics in the first half of Game 4, the Heat came out looking different. They had, perhaps, taken their halftime chat with Spoelstra to heart.

“The way we came out in the first half, we weren’t as committed as we can be,’’ Spoelstra said. “That’s the way you have to be against this team. You have to collectively be willing to get into the pit and get your hands dirty for however many minutes it may be.’’

It worked, too, as the Heat climbed back into a game in which they had been down by as many as 18 points. They tied the score in the fourth quarter, forced overtime, but didn’t quite have enough in the end.

As Spoelstra said, “In the second half, we got into the grind, into the fight.’’

Still, their defense was where it needed to be, finally at the required level to combat Rajon Rondo and the Boston offense.

The Celtics had scored 34 points in the first quarter, 27 in the second, but managed only 12 in the third quarter when the Heat turned up the pressure.

“That’s because we decided to play some defense, man,’’ Dwyane Wade said. “They were carving us up earlier in the game. Seemed like they got every option. They probably had four, five people in double figures or close. It’s hard to beat the Boston Celtics. Can’t nobody beat the Boston Celtics when they have that many people being effective.

“You’ve got to try to limit as many options as possible, which we didn’t do early on. But in the second half, I thought we did a great job.’’

With the program

Spoelstra has watched Mario Chalmers become a valuable piece of the Heat, if less heralded than a couple of other members of the team, since Chalmers arrived from Kansas the same year the coach took over the team.

“You love to have guys that grew up in your system, go through the ups and downs, grow as a young player and see them come into their own,’’ Spoelstra said before Game 4, in which Chalmers contributed 12 points and four assists in 35 minutes. “He’s making great strides with not only his game but his maturity, his professionalism. It’s been really gratifying to see that.’’

Not that it’s easy to be the point guard of the Heat, even if he does generally have multiple good options. It takes a strong player to be able to take charge of the offense on a team with Wade, James, and Chris Bosh.

“You better have some guts and you better have some confidence to be the point guard on this basketball team,’’ Spoelstra said. “Rio’s come a long way. He wasn’t a natural point guard, he wasn’t their point guard in college. So he has come a long way. Those qualities allow him to play with big players, because he thinks he belongs out there on the court.’’

Bosh still sidelined

Spoelstra started off his talk at shootaround Sunday by saying that Bosh (abdomen strain) was still “indefinite.’’ He didn’t even wait for the question to be asked . . . The coach was asked to describe the matchup with the Celtics’ Doc Rivers on the sidelines. “I don’t think people are paying any kind of money to see that matchup,’’ Spoelstra said. “I have incredible respect for Doc. He’s a great coach. I’ve had some opportunities to spend a little bit of time with him during the summers. He’s a great X’s and O’s guy, but what really separates him is his ability to manage personalities. That’s the part that I was interested in.’’

Amalie Benjamin can be reached at abenjamin@globe.com. Follow her on Twitter @amaliebenjamin.