At the start of the second half of the Cavaliers’ historic “Boston Massacre” rout on Friday night, TNT broadcasters Chris Webber and Reggie Miller already were dissecting what moves the Celtics can make in the offseason.

Before Game 2 of the Eastern Conference finals even had ended, debate on how the Celtics close the canyon that exists between them and the Cavaliers had begun. The Post reported last month Celtics coaches had interest in pursuing a trade for Carmelo Anthony at February’s deadline, but general manager Danny Ainge didn’t want to wipe out his 2017 summer cap space.

Now what? Some NBA executives at Chicago’s draft combine predicted the extent of Ainge’s offseason retooling hinged solely on whether his team was competitive with Cleveland and could take the Cavaliers to six hard-fought games.

Instead, the series has turned into a major embarrassment and black eye for Adam Silver’s two-team NBA. The Celtics look as if they don’t belong on the same floor as the Cavaliers, who posted two straight routs in Boston, including the 44-point blowout Friday.

The Post has reported the Knicks are interested in Boston’s defensive small forward Jae Crowder as a centerpiece in an Anthony deal. Crowder has been overwhelmed by LeBron James, so Ainge could be more apt to deal him. A 2018 first-round pick (the Celtics have two of them) would be icing.

The Celtics would need to add filler (perhaps free agent Jonas Jerebko in a sign-and-trade contract) to have the salaries work under the cap. However, Boston can absorb much of Anthony’s $31 million wage (which includes a trade kicker) with its cap space.

Of course, Ainge has other ideas. The Vertical reported Ainge wants to use his potential $30 million of cap space on Jazz free-agent forward Gordon Hayward, who played for Celtics coach Brad Stevens at Butler, but can get paid a lot more by staying in Utah. All-Star wings Paul George and Jimmy Butler likely will be on the market, too, but each of them would cost an arm and a leg compared with what the Celtics would give up in an Anthony deal.

Webber said Boston needs a power forward who can score on the block, and that is what Anthony can be in his very late prime.

Adding the No. 1 overall pick, either Markelle Fultz or Lonzo Ball, won’t be enough for the Celtics to close the Cleveland chasm. Ainge will engineer a major deal, and Knicks president Phil Jackson, who has made Anthony the scapegoat for his team’s woes, only can hope Hayward sticks in Utah.

Janis Porzingis, brother and agent of Kristaps Porzingis, met recently with Jackson, a source confirmed to The Post, after the Knicks big man blew off his exit meeting in April.

General manager Steve Mills didn’t attend the meeting because he was out of town, but it doesn’t appear anything was resolved between Porzingis and the team. Porzingis is upset at the chaotic nature in which the franchise has been run.

According to an NBA source, former Knicks point guard Pablo Prigioni is trying to decide whether to begin his coaching career in Spain or the United States before he engages in specific talks with the Knicks. The source said the Knicks extended an open invitation to Prigioni to talk about a coaching spot, likely as a developmental coach.

Prigioni began his apprenticeship as head coach of one of the teams in the Chicago draft combine 10 days ago and spoke with Knicks general manager Steve Mills. Prigioni told The Post in Chicago he might lean toward Spain for family reasons. Prigioni spent nearly a full season — Jackson’s first as team president — playing the triangle before requesting a trade to a contender at the deadline in February 2015 (he went to Houston).

Last weekend, Knicks associate coach Kurt Rambis, a 1980 graduate of Santa Clara, was the presenter for Steve Nash (1996) when the retired NBA star was inducted into the university’s Hall of Fame.

Rambis, a former WCC Player of the Year who won four NBA titles as a Lakers defensive forward, cracked up the crowd when he introduced Nash as “the best basketball player — from Canada — to ever attend the university.’’

Purdue sophomore PF/C Caleb Swanigan, the Big Ten Player of the Year, will work out for the Knicks on Wednesday, according to Zagsblog.com. He may return for his junior year and is slated as a second-rounder.

The Post reported last week Iowa State senior PG Monte Morris interviewed with the Knicks at the Chicago combine and reportedly will work out with the club June 8. Coach Jeff Hornacek is an Iowa State alum.

The Knicks have two second-round picks — 44 and 58. Swanigan and Morris are projected in the 40s.