The Boston Celtics were at full strength for just the second time this season Sunday while suffering a 105-92 loss to the Oklahoma City Thunder.

It didn’t help. Boston scored just 27 second-half points on 20 percent shooting after leading by 10 points at halftime.

“I would say we didn’t play up to our level at all offensively in the second half,” center Kristaps Porzingis said. “I think some of those situations we’ve got to look at and just give each other more space, more freedom. Just more space. At the end we just need more space and to be smart when we have the opportunity, and work for each other. I don’t think we played selfish or anything like that. We just didn’t play good.”

The Celtics playing with their full rotation led to a host of interesting decisions from coach Joe Mazzulla. Luke Kornet (15 minutes) played more than the Sixth Man of the Year favorite, Payton Pritchard (11 minutes), who had a poor shooting night. Porzingis (29 minutes) also played more minutes than Al Horford (24 minutes) and both were used in double-big situations with Kornet.

Ultimately, Mazzulla did not play a reserve beyond Horford in the fourth quarter, sticking with his starters when the going got tough. That was a particularly bad formula because the starters had a -46.9 net rating per 100 possessions over 18 minutes.

On the flip side, Horford with the other starters had a +42.1 net rating in eight minutes. Looking at those numbers in a one-game sample size means little on a night when no shots were going in. But if one zooms out a little this season, a bit of a concerning trend is forming.

• Net rating for Porzingis with the usual starting five: -11.3 in 103 minutes (7 games)

• Net rating for Horford with the usual starting five: +22.7 in 206 minutes (12 games)

The Porzingis numbers are not exactly shocking given how much he’s been in and out of the lineup, but his inability to gain a rhythm with that group is telling. Boston’s offense and defense have taken a step back with him on the floor with the starters and it’s certainly worth monitoring over the upcoming few weeks amid a tough schedule. For comparison, the Celtics had a +11 net rating with that same group last year over 623 minutes.

On the flip side, Horford’s importance continues to grow even amid his age 38 season. The offense and defense remain elite when he’s on the court, and his production with that group is far superior to last year already (+2.7 net rating in 311 minutes).

Porzingis is and will remain the starting center for as long as he’s on this team and healthy. But it should become more of a conversation now about who exactly should be the crunch time center. Horford looks like the better candidate at this point.

Altogether, this remains an area worth watching as the Celtics continue through their toughest stretch.