OMAHA, Neb. — For many years, the Saturday of the Final Four was considered the best day in the NCAA men's basketball tournament.

However, that is no longer the case.

Now, the best day in the Big Dance is any of the four days on the first weekend. Take your pick, because the tournament's first four days are filled with enough mega-upsets, mild upsets and near upsets to blow up brackets and worry coaches.

The impetus behind this upsetting trend is the 3-point shot. Since the trifecta was introduced in 1987, it has become the currency of the underdog.

You've heard of a puncher's chance in boxing? Well, the 3-point shot gives the underdog a shooter's chance, especially in the pressurized atmosphere of the NCAA tournament.

In facing 14th-seeded Cal State Fullerton in its first-round game Thursday night at the Qwest Center, the third-seeded University of Wisconsin was up against the most dangerous underdog it could have faced. You see, the Titans have an intimate relationship with the 3-point shot, and teams that can bomb from the outside have given UW problems in the past.

While UW had the edge in size, depth and talent, Fullerton had the 3-point shot on its side. It was ranked sixth nationally in scoring at 82.6 points per game and was in the top 10 percent of Division I teams in 3-point baskets per game and 3-point field goal percentage.

That didn't even the sides completely, of course, but it was enough to turn UW's 71-56 victory over Fullerton into a real struggle. It also turned into a terrific sign for the Badgers because they survived against the Titans due largely to their perimeter defense.

It is obvious by now that this UW team lives and dies with its defense. The Badgers are ranked first in the nation, allowing 53.8 points per game.

But if coach Bo Ryan's defense has shown a weakness historically, it is in guarding the perimeter. UW's top defensive priority is to protect the rim and, if that is successful, to run at 3-point shooters and try to take them out of their comfort zone.

Despite that emphasis, 3-point shooters occasionally have gone off on the Badgers. It happened last year when UW was a No. 2 seed and fell to No. 7 UNLV in the second round. The Runnin' Rebels were 10-for-20 from 3-point range in that game.

Clearly, Ryan learned his lesson, because he wasn't about to let that happen this time.

In the first half, UW showed its defensive hand early. Scott Cutley, Fullerton's 6-foot-5 center, sank an uncontested 3 on the Titans' first possession. Their only other 3 of the first half came when Josh Akognon, their best outside shooter, pulled up on a fast break. All told, Fullerton was 2-for-8 from 3-point range in the opening half.

The trade-off for that was Fullerton had room to operate inside, something teams normally don't find against UW's defense. With the Badgers exerting more pressure than usual on the perimeter, nine of Fullerton's 12 first-half baskets came from the lane.

But even though the Badgers held only a 30-28 lead at the half, they had accomplished two goals. The game was being played at their pace and the Titans hadn't gone off from the 3-point line. Because of that, it was only a matter of time before UW wore down Fullerton and pulled away, which it did in the final 10 minutes.

Since advancing in the NCAA tournament is more about matchups than seeds, UW's defensive performance was a great sign for their future. Until Akognon started launching — and making — 3s from NBA distance late in the game, the 3 was never a part of Fullerton's offense.

Ryan said that had less to do with strategy than in the improvement made by perimeter defenders Trevon Hughes, Jason Bohannon and Joe Krabbenhoft this season.

"I think we've covered better this year," he said. "Some guys gained some great experience last year. Pop (Hughes) and Ja-Bo are two great examples and Joe is a better perimeter defender than he was last year. So add that to Michael Flowers and we're (better) at guarding the 3."

Clearly, this team plays defense better than any of Ryan's first six UW squads. The Badgers showed Thursday that they are capable of handling anything thrown at them — including the 3-point shot.