It was interesting watching them play together this season, but Marcus Smart’s eyes widened when he thought of what he and Jaylen Brown might be able to accomplish together in the next several years.

Smart envisions lob passes to Brown on the fast break and the two of them working in tandem on the defensive end to bedevil opponents. A 23-year-old in his third season and a 20-year-old rookie, they seem built to play with each other — a big guard and a rangy wing who can both defend multiple positions.

Pressed into a starting role in Isaiah Thomas’ absence, Smart has been immersed in the Eastern Conference finals battle with Cleveland. But he’s liked how Brown has developed and how hard he’s worked after practices.

So he’s eager to see what can be and what they can be as a duo.

“Oh, I definitely am,” said Smart. “Definitely. We’re not too far apart in age. I’m ready. I’m excited for him and excited for what his future is.

“I’m looking forward to playing with him and seeing what we can do together. He’s an athletic guy and he plays hard. We’re going to work even better together as we go along.”

The next big step in Brown’s progression will come this summer as he takes what he’s learned as a rookie and uses that to refine his offseason workouts. Smart is expecting much more from him next year.

“Oh, no doubt,” he said. “He’s athletic, and his jumper’s coming along. He’s a really good offensive threat, and not only that, but at the defensive end he’s been working his tail off.

“I saw a quote from him where he said, ‘I’m going to come in and be ready to guard whoever, including the waterboy.’ That says a lot about him and his character and his willingness to devote himself to the team and sacrifice for the team. That’s only going to make him a better player.”

Amir Johnson has seen quite a bit in his dozen NBA years, and it’s Brown’s willingness and desire to fit into what best helps the operation that impresses him most.

“Rookies usually have one mindset and that’s just scoring and trying to play their own game,” said Johnson. “But for him to take a big role and play well in the playoffs, man, it just shows you how far he’s going to go. Teams need that. Especially contending teams that really want to win, they’re going to have to have guys that are mentally prepared for games like this. And to be playing in those kind of games now is big-time for him.

“The sky’s the limit for him. To have your first year and be on this big stage is definitely giving him a lot of experience. He sees it firsthand, and he’s going to know what it takes to get to this level.”

Johnson figures this playoff run has given Brown a head-start on what he encountered as a young professional.

“My first three years in the NBA, I was in the D-League, and that didn’t stop me,” Johnson said. “I actually asked to play in the D-League just to get better, and 12 years later I’m still here. I’m still here grinding. The work is nonstop.”

It’s not hard for Smart to recall how important getting a year under his belt was to his own progress.

“It was a different feeling,” he said. “Being able to experience it makes all the difference as you go forward and get ready for your second year.

“It’s tough when you come right out of college. When you’re back in school, you’re playing so many minutes and you always have the ball in your hands. Then you go to trying to figure out how to play with other guys that are in the same position as you. It’s tough when you have to take a back seat, but I feel like once you get that first year in — and sometimes it might take that second year, too — it changes.

“But for a lot of guys, when you get that first year out of the way, coming into your second year you feel more comfortable. He’s getting great experience in this atmosphere. Being able to be put in the fire right now, that’s going to help him a lot.”