Justin Bieber may need to work a little harder on his focus.

Sure, keeping it together on a massive outing like his “Purpose” tour night after night is tough. So it’s understandable that his mic was at his side Wednesday night when he was supposed to be singing, making it clear that he was lip syncing for at least part of the show.

And there were points when he was standing still while his phalanx of 12 dancers were around him.

But Bieber forgot to sing his most recent No. 1 single “Love Yourself” in the middle of his show.

“I got a little ahead of myself,” Bieber said, as the stagehands rushed to return the sofa they had already removed as well as tuning his acoustic guitar again. “Should I skip it?”

Of course, the capacity crowd screamed “No!” And, to his credit, Bieber, a little red-faced, delivered a strong version of the song.

advertisement | advertise on newsday

Though Bieber pulled his career out of a tailspin with the recent string of three No. 1 hits from his album “Purpose,” his concert at Barclays Center Wednesday night showed that his career rebound hasn’t solved all his problems. (Bieber returns to Barclays Center again Thursday, much to the chagrin of New York Islanders fans whose playoff game is delayed until Friday to accommodate the show.)

The “Purpose” tour is quite the spectacle, with its multilevel stage and elaborately choreographed routines. But Bieber ends up being the center of attention and, at times, the weakest link.

He opens the show in a massive glass box, and in one of the night’s best moments, dances in a circular video screen that looks like he’s trapped in a cage. No need for college-level performance art classes to figure out what that means.

The show has its moments. With the upbeat “Get Used to It” seeming primed to be his next chart-topper. Bieber looks energized when he’s doing flips on a giant trampoline during “Company.” And the tropical-tinged dance numbers like “What Do You Mean?” and “Where Are You Now?” hold up well, giving his faithful fan base plenty to scream about. They want him to succeed and most everyone loves a comeback.

But before that becomes a secure possibility, Bieber needs to find his “Purpose” a little more interesting.

SET LIST: Mark My Words / Where Are Ü Now / Get Used to It / I’ll Show You / The Feeling / Boyfriend / Untitled / Home to Mama / Love Yourself / Been You / Company / No Sense / Hold Tight / No Pressure / As Long As You Love Me / Drum Solo / Children / Life Is Worth Living / What Do You Mean? / Baby / Purpose // ENCORE: Sorry