It looked like little more than a slip, a buckled knee and a player falling gently to the floor. There was little indication on Feb. 24 how much the season-ending injury to Purdue's Robbie Hummel would have repercussions across college basketball. Has one injury ever inflicted such postseason chaos and shuffled expectations like this? Purdue was 23-3, ranked third in the country and in position to be seeded first in the NCAA tournament when Hummel, a 6-foot-8 junior who did not lead the team in points, rebounds or assists, tore his anterior cruciate ligament against Minnesota. Purdue had beaten four top-10 teams but lost two of its final five games, the last by 27 points to Minnesota. That forced the committee that slots teams into the tournament bracket to weigh Purdue's post-Hummel outlook against its meaty season-long resume, an unprecedented bit of prognosticating. It handed Purdue a fourth seed in the South Region and placed the Boilermakers opposite No. 13 Siena, which has pulled off first-round upsets each of the past two seasons. Just like that, Purdue (27-5) went from a national-title favorite to an uncomfortable role as a hulking first-round near-underdog. The popular online bracket contest at espn.com showed that more than one-third of entrants picked Siena (27-6) to beat Purdue. Even President Barack Obama picked Purdue to lose. 'The only thing we can do to prove anybody wrong is to win basketball games,' the senior guard Chris Kramer said. Hummel, who had knee surgery and is expected to be off the court for up to six months, is a do-it-all swingman who averaged 15.7 points and 6.9 rebounds per game. Purdue considered Hummel a sort of glue to bind together the talent of the 6-10 center JaJuan Johnson, the 6-4 guard E'Twaun Moore and a relatively anonymous supporting cast. 'Rob's one of the best players in the country,' coach Matt Painter said. 'His strength really lies in his intangibles. He understands how to play, he understands what's going on. He's very coachable, he's tough, he can guard a lot of different people. It's been an adjustment for us.' Hummel did not make the trip to Spokane, Painter said. Painter said he told his team, 'Let's learn how to play basketball with the guys we have.' The contender-to-presumed-bust transformation is similar to what happened a decade ago with Cincinnati, considered a certain No. 1 seed and title contender until Kenyon Martin, the national player of the year and soon to be the first overall pick in the NBA draft, broke his leg in the first game of the Conference USA tournament. The selection committee seeded Cincinnati second. The Bearcats lost in the second round to Tulsa. Yet this year's committee dropped Purdue much farther into the murky depths of the bracket. Dan Guerrero, the committee's chairman, noted that Purdue played several games without Hummel. 'They're a different team,' he said. Plenty of high-seeded tournament teams had a couple of losses at the end of the season. But Hummel's stumble seemed to knock the rest of the team off balance. In the five games since Hummel's injury, Moore and Johnson have seen their scoring averages drop amid double-teaming by opponents. Moore is 21 of 70 from the field (30 percent). Purdue, forced to play a much smaller lineup, has been outrebounded by 194-140. Against Minnesota in the conference tournament, the Boilermakers scored 11 points in the first half, were outrebounded by 50 to 26, and lost, 69-42. 'When we got our seed and were knocked down a little bit, we didn't begrudge the committee because they did it,' Painter said. 'I thought it was accurate and I thought it was fair. But we also gave them a reason to do it by the way we played against Minnesota.' The issue might be moot had Purdue been slotted to play a different No. 13 team -- Wofford, for example. But Siena beat fourth-seeded Vanderbilt in 2008 and No. 8 Ohio State last year. Siena players, as opposed to those on Purdue, now feel the unusual weight of expectation, even from the president. 'He knows what we're capable of doing, and hopefully we're going to prove him right,' guard Clarence Jackson said. Siena over Purdue? It took just one slip on a drive to the basket for everything to change. Now there is one team feeling like an underappreciated underdog. And another worried about complacency. Guess which one is which. 