SAN JOSE -- When push came to shove this season, a Cal basketball team without much innate aggression learned to give as much as it takes.

Rediscovering their physical side after back-to-back defeats will be critical when the Golden Bears open NCAA Tournament play Thursday afternoon against UNLV at HP Pavilion.

"We have to be the aggressor from the beginning," sophomore forward David Kravish said. "That's how we went on the run that got us to this point. Whether they were bigger, faster or could shoot better than us, we kept them moving backward while we kept moving forward."

The lesson of aggression was not easily absorbed by the Bears (20-11), who lost 76-75 at home to the Runnin' Rebels (25-9) on Dec. 9 in Berkeley when Quintrell Thomas converted an airball into the game-winning putback.

Strong and fast, UNLV will test Cal with defensive pressure and aggressive offensive rebounding. The Rebels boast 250 steals and 197 blocked shots and will work hard to impose their will.

"I don't think we have physical kids by nature," Cal coach Mike Montgomery said. "It's hard for them to change the way they are naturally."

That translated at times to playing soft, especially on defense.

Recalling early losses to Wisconsin and Colorado in which they allowed 81 points each, Kravish said, "It was obvious we needed a mentality change. The body language was bad, we were getting beat everywhere on defense."

But for an impressive seven-game stretch through most of February, the Bears played with a defensive toughness that shot them from near irrelevance in the Pac-12 to the brink of a conference title.

Starting with a 77-69 win at then-No. 7 Arizona, Cal ran off seven straight victories, also knocking off UCLA and Oregon. The Bears held their foes to 56.7 points per game and 33.5-percent shooting during the run.

The Feb. 17 home game against USC got national headlines when Montgomery shoved star player Allen Crabbe during a timeout, hoping to create a comeback spark. The Bears, down by as many as 15 points in the second half, rallied behind Crabbe for a 76-68 win.

But Kravish said the turnaround actually began two weekends before, with the Bears trailing by 12 points early in the second half against Oregon State and at risk of dropping to 3-5 in Pac-12 play.

Cal held the Beavers to 33-percent shooting in the second half to win, then put a serious defensive squeeze on Oregon in a 56-54 home win.

"That really clued us in to what we had to do," Kravish said.

It's not just the Rebels' big front line, featuring 6-foot-8, 240-pound freshman Anthony Bennett, that will challenge Cal. The style of officiating in the postseason will require the Bears to muscle up.

"Historically in the NCAA tournament there has been more contact and you've got to play through it," Montgomery said. "It's just an adjustment you need to make."

The Bears lost their way defensively a bit the past two games, losing 83-70 at home to Stanford in a regular-season finale that could have given them a piece of the conference title. Then they fell 79-69 in overtime to Utah in the Pac-12 tournament.

But point guard Justin Cobbs said everyone on the team recalls the sudden end after an NCAA First Four loss to South Florida last year.

"It's a feeling that's still fresh in my mind," he said. "It's 40 minutes and I think we're very conscious of what's at stake and the opportunity in front of us."

For more on Cal sports, see the Bear Talk blog at ibabuzz.com/beartalk. Follow Jeff Faraudo on Twitter at twitter.com/CalBearsBANG.