ATLANTA — It’s the age-old question: What happens when the immovable object meets the unstoppable force?

College hoops fans get to find out on Saturday, when the airtight UCLA defense attempts to put the clamps on a Florida offensive juggernaut that seems poised to win its second consecutive national title.

But it’s the Bruins who may have added motivation in the second game of this weekend’s Final Four doubleheader. They were thoroughly dominated by Florida in the national title game a year ago, but they’ll get a rematch Saturday against the same Gator starting five.

Nonetheless, coach Ben Howland won’t have any of the revenge-as-motivation talk.

“I think the motivation is to win,” is all he allowed in Wednesday’s press conference call.

Wherever their inspiration comes from, the Bruins will have their hands full against what is, by acclamation, the nation’s most talented team. Florida looked ininterested at times during the regular season, but breezed through the SEC tournament and was never seriously challenged in the East regional.

With two likely NBA lottery picks in center Joakim Noah and power forward Al Horford, and a third sure-fire first-rounder in slippery small forward Corey Brewer, the Gators’ frontcourt is a huge challenge for any opponent. But for the Bruins they’re especially difficult to handle because UCLA doesn’t have the size to match-up. Six-foot-nine-inch center Lorenzo Mata and 6-foot-8-inch forward Luc Richard Mbah a Moute will both be giving up inches and pounds to their Florida counterparts.

UCLA has to make up for it is with their quickness and defensive concepts. Our Jonah Keri tabbed UCLA as the nation’s best defensive team on Monday, and I concur. Despite modest size and shotblocking, the Bruins’ quickness, discipline, and teamwork at that end is truly something to behold.

This speaks well for Howland’s talents as a coach (his teams at Pittsburgh showed similar traits), and the result is a jarring transformation for long-time UCLA watchers. In the past we got used see talented-but-underachieving Bruin teams flame out against lesser squads; now it’s UCLA who is the overachiever, as it showed in beating a vastly more talented Kansas team in the West regional final.

However, the Gators are on a different level. They’re the nation’s top offensive team by the same metrics that had UCLA no. 1 on defense, a fact that requires little more than open eyes to verify. All five starters average in double-figures, and three-point shooting aces Taurean Green (40.4% on 3s) and Lee Humphrey (45.5%) penalize opponents who double-team Horford and Noah. In addition to their individual talents, the Gators play with admirable unselfishness and have achieved a level of cohesion few college teams can emulate.

The UCLA approach will be to kill the body and hope the head dies as a result. Led by point guard Darren Collison, they plan to use constant man-to-man ball pressure on Green and Humphrey —neither of whom has been confused with Marques Haynes — to prevent the ball from ever reaching Noah and Horford on the blocks. That’s why Florida coach Billy Donovan said that avoiding turnovers against the UCLA guards was one of his two major concerns on Saturday (the other is free-throw shooting — the Gators missed 15 of them in their regional final win over Oregon Sunday).

Collison’s pressure isn’t the only concern. Mbah a Moute and shooting guard Arron Afflalo also are outstanding individual defenders, with the former doubling as a ball-hawking pest who averaged 1.7 steals a game from the power forward spot. Additionally, UCLA’s superior depth could help it wear down the Gators in the second half — especially if they create foul trouble situations that force Florida to use its suspect bench.

But for the Bruins to pull the upset, they need their spotty offense to show up. UCLA hasn’t scored more than 70 points in a game in over a month, and in last year’s final it was an inability to score that doomed the Bruins.

One matchup seems especially important, as the long-armed Brewer completely shut down Afflalo a year go. But Howland thinks his leading scorer may be up to the challenge this time because of his expanded game. “He’s better off the bounce this year,” he pointed out, which should make it harder for Brewer to focus on shutting down Afflalo’s catch-and-shoot game.

Florida’s big guys will have the freedom to roam and contest shots when the UCLA guards drive because neither Mata nor Mbah a Moute are scorers. To counter that, the Bruins’ big guys need to pound the offensive glass and make Florida pay by getting easy putbacks. Otherwise, it’s a 3-on-5 battle that will have UCLA fighting uphill all game.

On the Florida side, this week’s big news item doesn’t involve its players, but rather the head coach. Donovan has been facing non-stop rumors that he’s going to leave for Kentucky ever since Tubby Smith bolted the Wildcats for Minnesota last week. He issued a fairly tepid denial on Wednesday, saying only “My focus is on our team, our program and our opportunity.”

Of course, it would be a much bigger issue if any of his players were planning on being in Gainesville next year. Humphrey and top reserve Chris Richard are seniors, while Horford, Noah, Brewer, and Green all look headed for the NBA after the season. Thus, unless Donovan is on the phone with Kentucky during the game, I can’t imagine it will be much of a distraction.

That’s just one more reason to think that the Gators’ run of dominance will last at least two more days. UCLA is talented and disciplined enough to hang tough with them for a half, especially if fouls become an issue. But ultimately, I think we’re headed for a repeat of last year because the Bruins lack the offensive weapons to keep pace with the Gators. For a second time, the unstoppable force will prevail over the immovable object.

Florida 68, UCLA 63

jhollinger@nysun.com