The Celtics have until Monday to sign Marcus Smart to a rookie contract extension, something the guard would dearly love.

But there’s one problem. Smart confirmed Monday night that he hasn’t heard from the team on the matter. Should the Celts not extend Smart, he will become a restricted free agent next summer, and undoubtedly an in-demand restricted free agent.

Some teams are indeed wrapping up their rookie contract players. Philadelphia, for instance, on Monday signed Joel Embiid – he of the 31-game career – to a maximum extension worth $148 million over five years.

Smart can’t help but notice numbers like this.

“Me and my agent haven’t heard anything from the Celtics,” he said after the 113-96 exhibition win over Philadelphia. “And, like you said, a week with the deadline and everybody else out here, and you’re seeing everybody else’s numbers and things like that, so we’re just kind of waiting.

“I would love to (stay). I would love to. I love Boston. I was drafted here. I’m the longest tenured Celtic. The city is great, this organization is great. I would love to be here. Like I said, we’re just waiting.”

EITHER KYRIE Irving, Gordon Hayward, Al Horford and Marcus Morris, all inactive Monday, need the rest, or the Celtics’ second unit needs some extended quality time on the floor.

Brad Stevens chose the latter as his reason for starting a bench-heavy lineup in the second exhibition game in four nights against Philadelphia. And Stevens’ latest chemistry project is moving along nicely.

Minus one drawback – Aron Baynes sprained his left knee in the first quarter and didn’t return – the second team had its way all game. Its lead hit a peak of 34 points in the third quarter.

Terry Rozier, often matched against Sixers rookie and No. 1 pick Markelle Fultz, wrapped up an efficient, sometimes dominant night with 15 points on 5-for-8 shooting, 10 rebounds, six assists, one steal and one block.

Not to be outdone, Smart began the game launching from downtown with a 2-for-3 first-quarter performance, and finished with 12 points, six rebounds and two steals.

In addition to losing 20 pounds in the offseason, Smart appears to have improved his oft-lamented 3-pointer. He’s now 7 for 12 in three preseason games.

As for Baynes, he was diagnosed with a hyperextended left knee. His status for Wednesday’s exhibition finale in Charlotte is unknown.

The Celtics and the trainers in their new performance department continue to follow a slow course where the implementation of Morris is concerned.

Morris missed Monday night’s game – his second since joining the Celtics last Thursday – and there is not a firm date for the 6-foot-9 forward’s debut, according to Stevens.

“I don’t know the answer to that. That’s a good question,” Stevens said. “It’s something that, along with our training staff, we’ll talk about every day. But today was just, he went through a good workout this morning and (will) progress appropriately.”

Morris recently said that he wants to lose approximately 10 pounds, though Stevens doesn’t sound worried about the forward’s conditioning.

Ultimately, he may emerge as the starting power forward.

“For the most part I feel like he looks pretty good. That may be what he feels personally,” Stevens said of Morris’ weight-loss goal. “But I think it’s partly just getting back into the routine and rhythm of things.”

Morris’ arrival was delayed while he stood trial in Phoenix with his brother for assault. They were found not guilty.