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Sometimes a man feels he has something left to prove.

The reasoning was just that simple when Creighton's Doug McDermott and Oklahoma State's Marcus Smart announced they would pass on the NBA draft and return to school.

McDermott said he wants to measure himself against more athletic and physical opposition in the Bluejays' first season in the Big East. Smart said he didn't want to end his college career on the sour note he and the Cowboys struck in the NCAA tournament.

Something else brought the first-team All-Americans back.

"You're only a college student once. You'll never get those four years back," McDermott said. "Some guys just like being a college kid."

Among other top players returning this season are Michigan State's Gary Harris, Ohio State's Aaron Craft, Louisville's Russ Smith, Syracuse's C.J. Fair and Arizona State's Jahii Carson.

McDermott is looking to become the 11th player to be a first-team All-American three straight seasons. The last two were Patrick Ewing of Georgetown and Wayman Tisdale of Oklahoma from 1983-85.

McDermott moves into the restructured Big East after dominating the Missouri Valley Conference. He, Oscar Robertson and Larry Bird are the only three Valley players to score 2,000 points in their first three seasons.

The versatile 6-foot-8, 225-pound senior forward was the nation's second-leading scorer at 23.2 points a game last season and is the unanimous pick as the Big East's preseason player of the year.

Having done about all he could in the Valley, would McDermott have come back to school if the Bluejays weren't going to the Big East?

"That's a hard question," he said. "It's no knock on the Valley, because there are great athletes in that league, but I'm going to face more great athletes in the Big East and I think it will prepare me for what comes next."

Interestingly, Doug McDermott will go into his final college season with the distinction of being the indisputable best walk-on player in the country. He announced last spring he would give up his scholarship to make room for the return of starting guard Grant Gibbs, who surprisingly was granted a sixth year of eligibility for medical reasons.

The Bluejays already were at their scholarship limit when the NCAA's decision came down. Greg McDermott, Creighton's head coach and Doug's dad, said he would gladly pay upwards of $40,000 for Doug's college costs to keep Gibbs in the fold.

Doug McDermott and Smart talked about their decisions to return to school when they were together at July's USA Basketball mini-camp in Las Vegas. They were the only college players among the pros at the camp, which helps identify future members of Team USA.

Smart said it was difficult for him, having just turned 19, to weigh the pros and cons and then explain his decision to people who couldn't understand why he would pass up a pile of money.

"It was the most difficult thing in my life," Smart said.

The 6-foot-4, 220-pound sophomore point guard was the Big 12's player of the year last season, and the 2013-14 preseason player of the year, after averaging 15.4 points, 5.8 rebounds and 4.2 assists. Just as important were his court presence, leadership and competitiveness.

He said he's coming back to improve on his 1.3-to-1 assist-turnover ratio and field-goal shooting of 40 percent overall and 29 percent on 3-pointers.

There also was that last game, the 68-55 loss to 12th-seeded Oregon in Oklahoma State's NCAA tournament opener. Smart was out of sorts all game, missing 8 of 13 shots, committing five turnovers and injuring his right wrist in the second half.

"I didn't even start touching the ball until May," Smart said. "I couldn't even do workouts because I couldn't touch a ball. It was that bad. And I didn't think me or our team gave it our all against Oregon. It left a disgusting taste in our mouth."

Smart might have been one of the first three players taken in the draft, yet he wanted to give it the old college try for one more season.

That's to be admired, coaches say.

It used to be that only projected lottery picks would leave school early, Michigan State coach Tom Izzo remembered.

"Right now if you're breathing, you've got a pulse and you can make a shot, you think you should come out," Izzo said. "So it's changed. It's changed a lot."

Izzo had two potential first-round picks who returned to school in Harris and Adreian Payne and, because of that, the Spartans are picked by many to win the Big Ten.

Creighton's McDermott was pegged to go late in the first round or early in the second, mostly because of uncertainty about where he would fit in an NBA lineup.

He's among four returning starters for the Bluejays, who are picked third in the Big East. If he can hold his own physically and put up the same numbers in his new conference, he'll surely enhance his draft value. Of course, there's always the risk of the opposite happening.

"Life is too short to think about what could happen," McDermott said. "If something happens and it hurts my stock a little, so be it. I stuck it out for another year for a reason, and that's just to win games and be around these guys for another year."

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AP Sports Writers David Skretta in Kansas City, Mo., and Larry Lage in East Lansing, Mich., contributed to this report.