BOSTON — Terry Rozier smiled as he spoke of Al Horford.

“He’s a big help,” Rozier said. “He’s going to set screens to get you open, he’s going to get himself open, he’s a big plus for our team.”

The glint in Rozier’s eyes grew a bit brighter when he added, “He’s playing young again.”

Old Al Horford, all of 31, laughed when the line was repeated to him a short time later after the Boston Celtics had beaten Toronto, 95-94, for their 12th straight win.

“I don’t know if young Al Horford played like this, to be honest,” Horford said.

It would be hard for anyone to play as Horford did Sunday under his circumstances. He missed the previous two games in the NBA’s concussion protocol, but there he was in the first quarter backing down Serge Ibaka to score, then driving in hard from the left for a dunk. Horford took nine shots and made eight of them on the way to 21 points, three rebounds, four assists and two steals in 33 minutes. He hit his only 3-pointer and is now shooting 48.7 percent from beyond the arc for the season.

And with the game on the line late, he switched to DeMar DeRozan and forced the Raptors’ star into one of his two key misses in the last 20 seconds.

“You know, it’s been years of just working on my game and trying to play this new way,” Horford said. “This is the style the NBA is shifting toward, and it’s taken me a couple of years to get comfortable and play like this.

“Young Al Horford couldn’t shoot 3s.”

Young Al Horford aside, last year’s Al Horford wasn’t this assertive with his offense until maybe the playoffs. But while he’s still facilitating for others and playing the right way, he’s also quicker to the trigger, whether it’s an outside shot or a drive.

“Definitely,” said Marcus Smart, who got the start for Kyrie Irving (facial fracture) and responded with 14 points and nine assists. “That’s what we wanted from Al. His matchups are very tough, because they don’t know whether to put a regular 5 on him or a smaller guy. We try to exploit that. We want Al to look more for his (shot), especially in the post when it’s one-on-one. He has to look for it.”

At the start of the day, the Celtics were just looking for Horford to be comfortable, to not suffer any setbacks from the hit to the head he took last Monday in Atlanta.

“It felt good,” he said. “I was just happy to be out there with my teammates. It was hard for me to sit on the side and have to watch, and just going through a lot of stuff – a lot of flashbacks of last year (nine missed games with a concussion last November). I tried to stay calm and take it day to day and do everything that I needed to do. So I’m just happy to finally be back out on the court.”

There were headaches and other symptoms, “typical stuff, concussion stuff,” Horford said, but “it wasn’t as severe as last year. Last year it was hard for me to just be out with the lights, out in the arena. It would take me back to square one. This time it wasn’t that severe. I felt better, so I was confident that I was going to be OK.”

As for the early moves to the bucket?

“One of the things that I wanted to make sure that I was feeling right, that I was good,” he said, “and I just had to be aggressive.”

Said Smart, “He brought that spirit back. Al’s a very good offensive player that can go create for himself and others, and we need a bucket, we just ran our plays through him and he created for us.”

And looked younger.

“Al’s getting to the basket, dunking on guys, and he’s not grabbing his knees,” Smart cracked. “No, definitely Al’s playing young, and that’s the cool way to put it. I like that.”

Neither playing that way or even playing as well as he did after the two games out didn’t catch Coach Brad Stevens unaware.

“No, I mean, I’m not surprised,” Stevens said. “You know, obviously he missed a couple of days there and wanted to make sure he was in really good shape before he came back, but he’s done so much for us for so long. Nothing that he does on the court surprises me.”

As for Horford’s increased assertiveness, Stevens said, “Well, he only took nine shots, and he made bunch of them. We as a team needed to do a better job of finding him I think at times. They had a real focus on being there on his catch today. They switched a lot of his screens, they tried to take away his 3-pointer, you know, they tried to be there and make it really hard to get looks, and so we had to play through Al a little bit as a passer, too.

“Our offense needs to smooth out still, but he’s obviously going to be a huge focal point, and even more so when Kyrie (Irving)’s out.”

Raptors Coach Dwane Casey wasn’t surprised either.

“I think he did what we knew he was going to do,” he said. “He popped back, made some shots. He made some post-up shots that he normally makes. I don’t think he did anything different that we didn’t think he was going to do.”

Back across the hall in the Celtics’ dressing room, it was more about Al the Kid.