Kyrie Irving played Game 5 as if he had already left Celtics

Celtics guard Kyrie Irving had 15 points Wednesday on just 6-of-21 shooting.BARRY CHIN/GLOBE STAFF/Globe Staff

MILWAUKEE — Let the record show that Kyrie Irving physically checked out of the Celtics’ season-ending loss to the superior Bucks in Game 5 of the Eastern Conference semifinals with 8 minutes and 40 seconds remaining and his team trailing, 91-68.

Said record also shows he had 15 points on 6-of-21 shooting, including just 1 of 7 from 3-point range. He had one assist, one rebound, three turnovers, one change of sneakers at halftime (turned out the problem was not the shoes), and was minus-25 in the 116-91 loss.

It should have been embarrassing, all of it, not that he was going to admit it.

“Truth be told, there’s no time to be disappointed, you take your lesson, you move on,’’ he said afterward. “I know I won’t forget something like this, the taste of feeling defeat and in this kind of style . . . For me it’s just moving on to the next thing.”

The greater mystery, and one that will carry into the summer, is whether the free agent-to-be has checked out on the Celtics for good.

Or perhaps the better question is: When exactly did he check out on the Celtics for good?

When did Kyrie Irving, who we must now admit has the makeup to be the perfect New York Knick, decide this wasn’t the scene for him and this season’s cause wasn’t worth the fight? That moment absolutely came before the season’s final buzzer.

Irving was so bad in every way Wednesday, so disinterested-looking, that it should affect his national perception. He’s an extraordinary player, one who has hit a shot to win a championship, but he did so as the Robin to LeBron James’s Batman. As a leader, he makes a team’s collapse look like an inside job.

The only surprise was that he didn’t tear off his jersey when the game ended, the perfect I’m-outta-here visual, a la South Beach-bound James in 2010 after the Celtics eliminated his Cavaliers. Irving, quick to finger-point at younger players, is more like James than he ever realized when he played with him.

The final game of this Celtics season, which began with rafters-high hopes and ended with them drawing comparisons to the 2011 Red Sox as the most unlikable Boston team of this decade, was a debacle that would have been much worse had the Bucks not shot poorly for much of the game. The last time the Celtics played this poorly against the Bucks, it was the 1983 squad giving the impression they wanted coach Bill Fitch fired.

Wednesday’s performance was the worst of Irving’s four straight poor games in this series after the Celtics surprised the Bucks in Game 1. Irving made just 25 of 77 shots (32.5 percent) from Games 2-5, including just 5 for 27 (18.5 percent) from 3-point territory.

It’s tough to question an athlete’s commitment at any level, but especially when it’s a star of Irving’s magnitude and accomplishment.

But it wasn’t just the uncommonly poor shooting (he shot 48.7 percent from the field this season, excellent for a guard, and 40.1 percent on threes) that was so disappointing Wednesday.

The shot selection — stepback three after stepback three — was a fine tribute to a past-his-prime Allen Iverson, if that’s what he was going for. He did not get teammates involved (no assists in the first half), and his ancient alter ego Uncle Drew would have given a better defensive effort in Games 4 and 5. Irving’s disinterest Wednesday night was at times blatant.

Irving, who told season ticket-holders at the season’s commencement that he planned to come back and had an ad featuring him and his dad playing one on one under the banners at TD Garden and talking about his love for Celtics tradition, has carried himself recently like his idea of Celtics legends are Sidney Wicks and Curtis Rowe.

He has done an about-face on acknowledging any commitment to Boston — he told us in early February, as an annoying inconsistency that turned out to be a feature rather than a bug with this team, to ask him July 1 about his plans, July 1 being the date free agency begins.

He’s offered few clues since, other than his usual meandering and cryptic comments, which he delivered for five minutes or so after Wednesday’s loss.

“I want to make it Boston first, you know, safely,’’ he said after the game while dodging two questions about whether he will consider remaining with the Celtics. “See my family, decompress, do what human beings do.”

So cryptic. Here’s betting he won’t be so cryptic on July 1, when free agency begins. It’s not that Kyrie Irving looks like someone planning to leave the Celtics. He looks like someone that already has.