Celtics guard Marcus Smart reacts against the Cavaliers during Game...

Celtics guard Marcus Smart reacts against the Cavaliers during Game 3 of the Eastern Conference Finals on May 21, 2017, in Cleveland. Credit: AP / Tony Dejak

The Knicks have expressed interest in acquiring Celtics guard Marcus Smart, according to a league source.

The Celtics could make Smart available as they try to clear salary-cap space to sign Gordon Hayward to a four-year, $128-million deal. But if they can work out a sign-and-trade with Utah for Hayward, it’s unclear if the Celtics will have to or want to part with Smart, 23.

Forward Jae Crowder seems to be the Celtic most likely to go, and he reportedly has come up in sign-and-trade talks with Utah. But the Celtics are said to be looking for assets back from the Jazz. Celtics president Danny Ainge would want the same for the versatile Smart, the No. 6 pick in the 2014 draft, the source said.

Multiple teams have inquired about Smart, the source added. He will be a restricted free agent next summer.

It’s been speculated that it might take Willy Hernangomez and a first-round pick from the Knicks to get Smart, who averaged 10.6 points and 4.6 assists mostly coming off the bench last season. That would be a lot to give up. Hernangomez appears to be a Knicks building block. Moreover, the rebuilding Knicks might not want to give up a first-round pick — unless it’s for an impact player — because it could be in the lottery.

The Knicks probably would rather deal Kyle O’Quinn, but from the Celtics’ standpoint, if they want to cut payroll, it wouldn’t make sense. O’Quinn will make $450,000 less than Smart’s $4.58-million salary for next season. Hernangomez will make $1.43 million next season.

It’s no secret that the Knicks need backcourt help and a good perimeter defender. The 6-4 Smart has shown he can play both backcourt positions, but he’s more of a scorer than a distributor. He’s also a hard-nosed, tough defender. He guards his position well and also has been effective against bigger players, including 7-3 Kristaps Porzingis, who is nearly a foot taller than Smart.

The Knicks currently have 10 players on the roster, including Carmelo Anthony and Ron Baker, who hasn’t signed his new deal yet. Seven of them are frontcourt players. The Knicks’ most glaring need is a veteran point guard to mentor first-round pick Frank Ntilikina and Baker.

They have been in touch with the agents for Rajon Rondo, Derrick Rose and Shelvin Mack. Rose has met with the Bucks and was supposed to meet with the Clippers, but they reached an agreement on a two-year, $12-million deal with European point guard Milos Teodosic.

The Knicks haven’t done much in free agency other than lock up their own players. They came to an agreement on a new two-year deal with Baker, signed Ntilikina to his four-year rookie contract and inked undrafted rookie Luke Kornet to a two-way deal. That means Kornet, who played for the Knicks’ summer league team, can shuttle between the NBA and the G-League for up to 45 days and won’t count on their roster.

Dotson deal in the works. The Knicks have begun contract negotiations with second-round pick Damyean Dotson, a league source said.

Dotson, 23, impressed the Knicks in the summer league with his shooting, rebounding and defense. The 6-6 swingman, whom the Knicks took with the No. 44 pick out of the University of Houston, has the size and athletic ability to be a good defender.

Dotson had 20 points and nine rebounds Thursday, helping the Knicks (1-4) close out summer league play with a 91-72 win over the Heat. He shot 4-for-7 from three-point range.

“Damyean can really shoot the ball,” coach Jeff Hornacek said. “He’s athletic. I thought he showed he can really stroke it. He can stroke it from deep. Shooting is huge. Another weapon that can get out there on the court. We know if he gets an open look, there’s a good chance he’s going to make it.”