SAN JUAN, Puerto Rico — After watching his team lose to Minnesota on Friday, North Carolina coach Roy Williams insisted he doesn’t think about last season anymore.

But now that his Tar Heels have lost two in a row – and at 2-2 are off to their worst start since 2001-02, thanks a 72-65 loss to Vanderbilt in the Puerto Rico Tip-Off on Sunday – he’ll likely have to start answering a familiar question from last season’s 17-loss letdown: What’s wrong?

Although No. 8 UNC (which will certainly fall out of the top 10 rankings this week) came back from a 14-point first half deficit, it couldn’t close out against the Commodores (3-1). The biggest problems, Williams said, was the inability to grab key defensive rebounds down the stretch, and defensive breakdowns when Vandy forced the Tar Heels to play tight ‘D’ for long stretches.

But it’s also obvious, with three new freshmen and zero returning scholarship seniors, that Williams is still looking for the right combinations of players that can play consistent defense, take care of the ball, and score in the clutch.

“What I’m looking at is five guys who will play together as one,’’ he said after his team committed 22 turnovers and allowed the Commodores to shoot 63.6 percent in the first half. “We’ve got great kids; you know what they’re saying? They’re saying ‘I’ve got to do this, or I’ve got to score.’ And it’s not that – it’s ‘we’ve got to do it.’ … We’ve got to make better decisions on how tough we’re going to be, getting after loose balls, and when teams get second-half opportunities against us.”

Trailing 39-29 at halftime, UNC opened the second half with a 12-3 run, cutting its deficit to 42-41 on two Justin Knox free throws. The Tar Heels were more aggressive on both sides of the court compared to the first 20 minutes, taking advantage of Vanderbilt’s six turnovers and 1-for-5 shooting.

UNC finally took its first second half lead, 48-47, with about 11 minutes left, on sophomore Leslie McDonald’s shot in the lane. But with the score knotted 51-51 with 8:13 left, Vanderbilt put together an 8-0 run, taking advantage of three Tar Heel turnovers and making 4 of 6 free throws.

Carolina freshman Reggie Bullock (10 points) halted the onslaught with a 3-pointer to cut his team’s deficit to 59-54, then forward Tyler Zeller converted a three-point play to put UNC within a bucket. But it was as close as the Tar Heels got.

With freshmen Harrison Barnes, Kendall Marshall and Bullock on the floor – and starters Larry Drew II, John Henson (6 turnovers, 0 assists, 2-6 from the free throw line, 2 points) and Dexter Strickland (4 turnovers, 1 assist 6 points) on the bench – Vanderbilt padded its lead by burying a bunch of free throw and getting a layup by Jeffery Taylor that pushed its lead back to 65-58. Strickland and Drew were among those who checked back in with about two minutes left, but they couldn’t muster a comeback, either.

Henson, a starting forward, played only six second-half minutes, and 16 minutes total for the game – another example of Williams’ determination to find the correct combinations.

“The way I’m going to coach – you guys know me, I love getting five guys and playing them all year -- but you’ve got to deserve to play,’’ Williams said. “You can’t just go out there – and I took Dexter out for a long stretch there -- you can’t have 0 assists and six turnovers, you can’t have 1 assist, 4 turnovers. You cannot hurt your team, and you’ve got to play better.”

Zeller led the Tar Heels with 20 points and 10 rebounds, while Barnes (0-for-12 in Friday’s game) finished with 11 points on 4-for-12 shooting. Jenkins led Vanderbilt with 16 points.

Williams insisted that he is not discouraged with the Tar Heels, who haven’t had this many losses to open the season since Matt Doherty’s team started 2001-02 with three straight losses. And despite the questions that will likely be asked, Williams – and his players – say their performances don’t feel anything like last year.

“We’re better,’’ Zeller said. “We’re not where we need to be yet; we can’t be, we just lost. But I believe it is better than last year; hopefully it continues to get better and better over the season. But it’s something we’ve got to be able to change.”

Robbi.pickeral@newsobserver.com or 919-829-8944