NEWPORT, R.I. — The topic might be simmering on a back burner for now, but as soon as New Englanders decide who they want in the Red Sox pitching rotation for the playoffs, they’ll turn to the puzzle that is the Celtics starting lineup.

Beyond the given three of Kyrie Irving, Gordon Hayward and Al Horford, there is much to shake out as coach Brad Stevens chooses who gets to have their name and college announced before tipoff.

But to learn the answer to that question, it might be more important to first ask another: Who needs to be coming off the bench to make that second unit work properly?

The Celts know what they’re going to get from Irving, Hayward and Horford, and no doubt they want people with them who maximize their abilities. But it will be critical, too, to make sure the Boston side of the scoreboard keeps moving when the All-Stars take a break.

The C’s will be good — very good — when the primary trio is on the floor, but their ability to put teams away will be greatly enhanced if their pine people can take advantage of the opponent’s reserves. Construction of the second unit is, therefore, key.

“I think that’s going to have to come into the discussion for us,” Stevens said. “And the more you look at it with our youth, that’s really going to have to come into the discussion. So that’s why we’re not settled on anything yet. I mean, we need to have a second unit that complements each other just as well as the first unit. Obviously finding the right guys to complement Al and Gordon and Kyrie is one of the critical things now, but you know what? It may be better for guys that are in our top five and playing at the end of the game not to start, just from the standpoint of more opportunity with the ball and everything else. We’ll iron all that out.

“It’s never been important to me who starts, as far as it being the five best or whatever. It’s more how they complement each other and how they complement your best players that are going to get the majority of the attention.”

That view was on display when Stevens would fill in for an injured starter based more on the needs of the second string. And it was evident pretty much every other night as a Canadian continued to come over the boards well after the opening faceoff.

“Kelly Olynyk easily could have been a starter the last few years, but he was so unique as a backup big,” Stevens said of the 7-footer who took his outside shooting talents to Miami as a free agent in the wake of the Hayward signing. “He could be very unique and very good as a starter, too, but for us, it just gave us a different dimension when he went into the game.”

Now Stevens is left to figure out the dimensions of a rotation he must cull from a roster that includes just one starter and but four players overall from last year’s edition.

Looking at the starting five and all the possibilities, Stevens, after just the first day of training camp at Salve Regina, said, “Yeah, it might be tough.”

“They have to be guys who complement those three guys,” Stevens said of Irving, Hayward and Horford. “Ultimately that’s part of it. And yeah, it’s going to be tough. It’s going to be one of the challenges that we have.”

The Celtics have talent and uncertainty, the latter from the fact there will be a handful of people getting minutes this season who have yet to play in the NBA. Top draftee Jayson Tatum will undoubtedly be in the mix, and Guerschon Yabusele and Daniel Theis could find their way in as well. And Semi Ojeleye will make a run.

One issue will be how the Celts choose to play up front next to Horford.

“I think that there’s a couple of different ways that we can go with that,” Stevens said. “But I’m not settled on anything.

“I mean, we could go with another big like (Aron) Baynes. We could go with another big like Guerschon or Theis, or we could go more of a smaller lineup with a Marcus Morris next to him or Jayson or Jaylen (Brown) in those spots.”

The backcourt starter beside Irving would seem to be a battle between Marcus Smart and Brown, but that could evolve as the year goes along. Fortunately for Stevens’ well-being and the club’s chemistry, the opening five isn’t the issue within that it might be outside.

“It’s not that important at all really, to be honest,” said Smart, whose ballhandling and ability to trigger a break could make him a better fit with Irving. “Everybody on this team has once been a starter and played starter minutes, but we’re all interchangeable, so that starter role, everybody can do it.

“Whatever the role that this team wants us to do, we all have bought into it, and we’re going to do whatever we have to do. If that’s start, if that’s not, we do it.”

As attitudes go, that’s a good place to start.