It’s been hard to notice given the play of Terry Rozier, but yes — the Boston Celtics miss Marcus Smart.

Here’s some suggestive evidence the Celtics are indeed smarting without him.

Wins, losses, and Smart plays

In their last 11 games, the Celtics are 6-5, and struggled particularly over a 5-game stretch in which teams figured out some of Boston’s vulnerabilities without him.

With Smart in the lineup this year, they’re 32-17.

5 reasons Celtics miss #36

1. Toughness on switches and inside help.

Through January 23, the Celtics defense allowed opponents 42.1 points in the paint per game. In the next six games, that figure crept up to 44, and in the last six, it’s more than 47 per game.

2. The “wear-down effect.”

For most of the season, Boston has deployed a three-headed defensive monster of Smart, Rozier, and Jaylen Brown. The resulting “wear-down” impact was evident in the weak shooting, especially in the fourth quarter, by opposing guards. And it left Kyrie Irving with just a little more energy down the stretch.

Last year, we observed how that effect worked on John Wall, whose career stats against the Celtics are weaker than against almost any other team.

3. Hustle plays

Smart remains second on the team in both loose ball recoveries and drawn charges to Aron Baynes. His signature hustle plays helped turn near-defeats into victory against Dallas (the “sweet 16” win) and Houston (the game in which James Harden was actually called for an offensive foul.)

And, they have a catalyzing effect. That one is hard to measure. But it’s testified to by most of the Celtics players, and by Brad Stevens.

4. Rebounding assists.

Smart is one of the best team defensive rebounders on their roster, reflected in our in-house “rebound assist” measurement.

Smart isn’t a Rozier or Brown when it comes to actually grabbing the rebounds. But against opposing bigs and wings who need to be sandwiched or muscled out, he and Marcus Morris are the two best helpers on the parquet. When one or both of them is out, it shows up in opponent second-chance points — which have also surged over the last 11 games.

As for offense…. well, it’s hard to make the case that the Celtics miss his shooting — though it was slowly improving in December and January.

But there’s one key area in which the Celtics may get a jolt from his return at the “other other end of the floor.”

5. 4Q Marcus?

Even after missing the last 11 games — or maybe because of it — Smart is the only Celtic in the NBA’s top-20 for clutch-time NetRtg. (Minimum of 25 games with at least 2 minutes per game of “clutch time” play.)

His assist to turnover ratio at clutch time is 4.0 — third best in the league. His assist percentage in the crunch is 22.9 percent, trailing only Kyrie Irving on the Celtics.

Lesson? When Smart does come back, try not to cringe at every missed shot. It’s better than having to cringe at a turnover. And it’s likely to be followed up for by a great hustle play sometime soon.