Brad Stevens’s funky lineups might have cost the Celtics a win over the Spurs

Stevens decided to start the fourth quarter — when the Celtics could have built the lead and their momentum — with a lineup of Marcus Smart, Kemba Walker, Grant Williams, Robert Williams, and Javonte Green.

While this may have looked like a decent defensive lineup, it was offensively lacking, with Walker the lone consistent scorer and Smart able to offer only occasional spurts. That lineup started the quarter shooting 1 for 9 (with Smart and Walker combining for seven of the misses), and a 2-point lead turned into a 3-point deficit. The Spurs added two more buckets when Jayson Tatum replaced Walker.

It wasn’t that this lineup was necessarily unplayable. But it was a strange decision to start a quarter after you had just regained all the momentum. Walker pressed as he tried to carry the offense and faltered, while Smart didn’t help by missing three shots.

It didn’t mean the Celtics couldn’t come back and win, but the decision cost them the lead and forced them to rally. Stevens used 13 players in the game, 10 in the second half. Generally, NBA coaches like to pare their rotations to eight or nine players.

Stevens freely admits he’s still trying to find effective combinations, but using such an offensively deficient lineup to begin the fourth quarter — and keeping Tatum and Jaylen Brown on the bench — was the difference. The Spurs started the fourth quarter on an 11-2 run, and the Celtics led for only 32 seconds of the last 9:36.

“I think there will be some experimenting looking for different matches and lineups,” said Stevens. “We played Grant and Semi [Ojeleye] in the second [half]. We wanted to be bigger. They bring a physicality to the game. The guys that didn’t get in in the second half, there wasn’t anything they didn’t do in the first.

“There’s not a ton of separation there.”

Stevens is saying that with no bench players really standing out, he’s going to play all of them until somebody does. That could be painful to watch at times.

With Walker back in the lineup to join Brown and Tatum for the first time this season, Stevens started Smart and Daniel Theis, who picked up two early fouls (shocker) and then was replaced quickly by Tristan Thompson.

Carsen Edwards and rookie Aaron Nesmith were the next players off the bench after that, which was a curious decision but shows that Stevens is no longer pleased with Jeff Teague’s minutes. None of those three played in the second half.

The second-half lineup was productive for the most part, but the problem was the Celtics trailed by 14 at halftime, so Stevens’s lineup decisions needed to be dynamic. The Spurs ended the first half on a stirring 29-6 run, a stretch Stevens called “terrible.”

And his second-half rotations were for about 18 of the 24 minutes. But it was that six-minute stretch that cost the Celtics a chance to win. The putrid second period left the Celtics no margin for error, so Stevens needed to tighten his rotations and start the fourth quarter with his best lineup, not with Tatum and Brown on the bench.

But the Celtics are facing a quandary, because Stevens has no idea whom to trust on the bench from one night to the next. Teague was supposed to be a scoring sparkplug who could run the offense, but he’s failed to do either. Grant Williams is solid on defense but has regressed offensively.

Theis’s foul trouble, which is constant, limited him to 12 minutes, so Stevens had to use a lot of Thompson, which burned the Celtics in certain situations because the Spurs kept a big man in the paint at all times because Thompson doesn’t stretch the floor.

At this point, the Celtics are a bunch of jumbled pieces beyond Tatum, Brown, Smart, and Walker, and until Stevens can trust his bench, either Tatum or Brown needs to be on the floor at all times. It is understandable that Stevens was trying to give both of them a break for the game’s closing minutes, but the lineups without them aren’t good enough to maintain a lead in a tight game against a quality opponent.

“It’s been an interesting season,” said Brown. “We’ve had guys out, guys hurt, now guys are back and we’re still trying to put everything together.

“We had a lot of chances to win this game, even in the second half. We just couldn’t get stops. We could have for sure been better and we for sure should have won this game — but we didn’t.”

Gary Washburn can be reached at gary.washburn@globe.com. Follow him on Twitter @GwashburnGlobe.