With the game on the line, why wouldn’t Celtics coach Joe Mazzulla call a timeout?

It was thumbs down for Joe Mazzulla, who Celtics failed to get a shot off in the waning seconds of OT in Game 4.Barry Chin/Globe Staff

PHILADELPHIA — Joe Mazzulla hates timeouts the way I hate mushrooms.

We saw this again Sunday after Boston Strangler James Harden splashed a 24-foot 3-pointer from the right corner with 19 seconds left to give the 76ers a 116-115 lead in overtime of Game 4.

Timeout, right? Call everybody over, draw up the old Picket Fence Play, and let the Sixers get caught watching the paint dry as one of Boston’s mighty Jays hits the game-winner or gets fouled and makes a pair to clinch it.

Nope. That would be the conventional Brad Stevens, Hoosier Way.

Joey M trusts his guys and lets them play it out.

So we saw Marcus Smart with the ball and then Jayson Tatum with the ball, eating up the clock, getting double-and-triple-teamed, before finally kicking it out to Smart for a 3-point attempt in overtime.

Too late. And we don’t mean Sam Jones, “too late!’’

It was too late for Smart to get a shot off before the buzzer. The red light lit the backboard’s perimeter while the ball was still in Smart’s hand. So it didn’t matter that his shot ripped through the net. The game was already over. The Celtics had failed to get a shot off in 19 seconds, and they’d put the game in the hands of a dubious 3-point shooter.

When asked if this kind of trust is “empowering,’’ Tatum said, “I guess it’s empowering. We got a good corps of guys that know how to play under pressure … I probably could have got the ball to Smart sooner.’’

Within seconds of the chaotic close, Magic Johnson tweeted, “I thought Celtic’s Head Coach Mazzulla made a mistake not calling a timeout and setting up a play in the final seconds of the game.’’

Yeesh. Bad enough that Joey M is going to hear it from Green Teamers. Now he’s got a Laker nemesis piling on from cyberspace.

“That was the play,’’ said Mazzulla. “We just had to play with a little more pace. We had the right matchup. Jayson got downhill and made the right play at the rim. We just had to play with a little more pace there.’’

Swell.

The decision not to call timeout will haunt Mazzulla and the Celtics if they don’t win two of the next three games. He’s in danger of being the Jim Montgomery of Hub hardwood.

Al Horford (five blocks!) was encouraged after the loss and he’s not alone.

Jayson Tatum, seen here tying the game at 96 in the fourth quarter, shook off a slow start to finish with a team-high 24 points.Barry Chin/Globe Staff

I still like the Celtics to win this series. I don’t think I’ve been this certain about anything since telling you that Masataka Yoshida was a bad signing, or that the Bruins were a lock to win the Stanley Cup.

But it certainly would have been easier if they were coming home with a 3-1 series lead.

This was a fun game, worthy of the old battles between Wilt Chamberlain and Bill Russell, Julius Erving and Larry Bird. It was a game of redemption for Harden, who was being compared with Ben Simmons after making only 5 of 28 shots in Games 2 and 3. Harden was Andrew Toney-esque Sunday, scoring 42 to bookend his 45 in Game 1. League MVP Joel Embiid scored 34 with 13 rebounds and was guarded by everyone except Justin Champagnie, who did not play.

The Celtics took a hefty punch for three-plus quarters, trailing almost from wire to wire. Boston fell behind by 16 in the third and was still down 9 at the end of three. But the Celtics pushed ferociously in the fourth, blocking a bunch of shots and taking a 5-point lead with two minutes to play near the end of regulation.

Unfortunately, the end of regulation was a lot like the end of overtime. After a floater by Harden tied it at 107 with 16.1 seconds left, Mazzulla let ‘em play and we wound up watching Smart miss an open-look three at the buzzer to send the game into extra innings.

No timeout. No advancing the ball. No huddle to draw something up. And no Tatum or Brown taking the final shot.

Brown (23 points on 10-of-16 shooting), who took zero shots in overtime said, “I guess I got to demand the ball a little bit more. I thought good things happened when the ball was in my hand.’’

It’s a game the Celtics could have won. And I’ve got to wonder what Stevens really thinks about his stubborn coach’s late-game strategies. Mazzzulla at this hour presents as a guy who has too must trust in a talented group that’s still trying to achieve championship status.