Boston Celtics

The wait for some much-needed defensive help may be over for the Boston Celtics.

In a first-round series that’s seen their league-best defense completely shredded by the Bucks, that defensive boost could come with the potential return of Marcus Smart, who has been upgraded to ‘questionable’ for Tuesday’s Game 5.

“Marcus felt great over the weekend,” Celtics head coach Brad Stevens said after the team’s morning shootaround. “Still has to go through some things after our shootaround, and then we’ll see how he feels after that. If he feels good, then he’s been cleared physically to go. If he has any pain or anything comes up, then we’ll keep him out.”

Out of action since tearing a tendon in his thumb on Mar. 11, Smart’s upgrade came the night before the 24-year-old was scheduled to meet with a hand specialist in New York, and with Stevens confirming that Smart instead flew on Monday to seek early clearance for contact. And this potential move also comes on the heels of the C’s dropping two straight games to send this series back to TD Garden with the series tied at two wins apiece.

And unlike his first return from a thumb ailment, which obviously came with Smart at less than 100 percent despite an 11-game absence, Smart clearly does not believe like his thumb is holding him back from jumping back into action.

“I think the thumb, the surgery did its job,” Smart told The Boston Globe on Sunday. “Thumb is holding up well. I feel ready. I feel strong enough to get back out there. I’m just waiting on the OK.”

“He hasn’t played in a month and a half, so this is just an opportunity to come in and do what he does best, and that’s impact the game with his energy, his physicality, his savvy, and his skill,” Stevens said. “I think that when you’ve got a player of his caliber, he’s really excited to play. But at the same time, we’ll see how he feels.”

If Smart does indeed feel confident enough to return either tonight or for Thursday’s Game 6 — which remains up in the air, as Stevens repeatedly hammered home the fact that he would not play Smart if he felt any sort of lingering pain whatsoever — it will likely be to address the Bucks’ Khris Middleton.

Averaging 25.5 points per game (the 11th-most among postseason shooters) and shooting 61.5 percent from the field (as well as an absurd 62.5 percent from behind the arc), Middleton has downright devoured the Celtics through the first four games of this series. And the Celtics have been unable to focus their efforts on Middleton given their emphasis on slowing down Milwaukee superstar Giannis Antetokounmpo.

The Bucks as a whole are shooting the lights out in this series, too, with an NBA-best 54.2 field goal percentage.

Opponents shot just 43.0 percent with Smart on the floor this season, meanwhile, which stood as the seventh-lowest percentage in the NBA among players with at least 50 games played in 2017-18.

Game 5 can be heard on 98.5 The Sports Hub with coverage beginning at 6:30 p.m.