The Boston Celtics and Miami Heat are led by coaches with very different temperaments. Erik Spoelstra, the second-longest tenured coach in the NBA, uses his timeouts aggressively when things aren't going according to plan. Joe Mazzulla, Boston's first-year head coach, is far more conservative with his timeouts. He prefers to let his team figure things out on the floor so he can save those timeouts for late-game scenarios if he needs them.
Those stylistic differences were on full display in Game 1 of the Eastern Conference finals. When the Celtics used a quick 7-0 run to cut Miami's lead to five, Spoelstra called a timeout just 94 seconds into the fourth quarter in an attempt to swing the momentum of the stretch. It worked. Boston never got closer than four points the rest of the way.
Mazzulla had several similar opportunities to call timeouts in the third quarter. Boston led the game by nine points at halftime, but the Heat won the third quarter 46-25. Aside from a mandatory TV stoppage, Mazzulla didn't call a single timeout during Miami's onslaught. "I called two in the first quarter," Mazzulla said after the game, later explaining that he would have used one in the third quarter had he not spent two in the first. Boston ultimately didn't call a timeout of its own accord in the second half until the 3:19 mark of the fourth quarter.
Mazzulla got heated during the third-quarter timeout he was forced to take, and was caught on camera throwing his clipboard in frustration.
For new head coaches, one of the hardest elements of running a team is game management. There is no way to simulate it ahead of time. Spoelstra has spent the past 15 years mastering every element of the craft. Mazzulla is still learning on the fly, and Game 1 offered him a lesson from the veteran: conserve your timeouts in the first half because you're almost certainly going to need them in the second.