Joe Mazzulla criticizes every aspect of a game, regardless of its result.

Perhaps that trait was overlooked during previous Mazzulla-led teams. After all, 2025-26 is the first season in which the Celtics’ head coach is not directing a roster setup for title contention. He instead has unproven commodities attempting to stay in the postseason mix while waiting for their franchise superstar player to return. Accomplishing that requires a different level of scrutiny and execution than past iterations.

It doesn’t matter if the Celtics narrowly lose by two points to the 76ers or blow out the Grizzlies by 36 points. Mazzulla must stay on task.

“The process matters,” Mazzulla said on Friday’s Zolak and Bertrand. “Did you get the two-for-one? Did you get the last play of the game? Did you get the read that you wanted to get? Did you execute? But it’s also, did you end quarters properly? Did you defend the other team’s best player properly? Did you execute the game plan properly? Those plays are there in the Memphis game as well. You just have to stick to that process of getting better at all those.”

As the third quarter neared its conclusion on Nov. 11th at Philadelphia, the Celtics held a nine-point lead with 2.3 seconds left on the clock. Quentin Grimes received the inbounds pass before he dodged defenders while rushing up the floor, eventually launching an open half-court heave before the buzzer sounded.

Grimes’ successful 3-pointer cut the 76ers’ deficit to six points, and maybe more importantly, swapped the momentum to their side in front of their home crowd. It signified what was about to unfold, as the 76ers put together a fourth-quarter performance that yielded a 16-point scoring differential over the Celtics in the final 12 minutes.

It was enough to hand Boston a two-point loss.

Facing the Grizzlies less than a day later, a similar situation occurred. As the Celtics led by eight points during the first quarter’s closing seconds, Cedric Coward found himself open for a corner 3-pointer. He squared to the basket and fired from 24 feet out, threatening a momentum swing.

That shot just shows up in the box score as a missed 3-pointer from Coward. It won’t be scrutinized by most after the game, especially considering the Celtics won 131-95.

“We didn’t defend both of those the right way,” Mazzulla said. “It’s just one was the difference between a win and a loss, and one had zero impact on the game whatsoever. So those plays do exist in a close game, but they exist in every game.”

Evidently, the Celtics still need more time to learn how to adequately defend those possessions. Leading by three points against the Clippers on Sunday, the Celtics allowed an inbounds pass under the Clippers’ basket to fly through the air to Ivica Zubac at the opposite end’s free throw line. Zubac maintained control, tipping the ball out to an open James Harden, whose game-tying 3-pointer rimmed out.

Nearly another missed opportunity.

A season ago, the Celtics had the talent to outplay most of their opponents. Those mistakes were usually quickly rectified on the previous possession or occurred when the game was already out of reach. But this season?

That is how Boston risks turning wins into losses.

“We’re all going to focus on the last couple of possessions, but we gave up 15 points on second chance in the third quarter,” Mazzulla said after besting the Clippers, 121-118. “We’ve got a great look by Payton (Pritchard) in the quarter. We’ve got a layup by [Neemias Queta], and then we had a [Derrick] White pull-up shot. If one of those goes in, it’s a different game. So we’ve just got to continue to execute possessions throughout the entire game.”