The 12-man U.S. Pan American Games basketball roster will be filled with college players.

Argentina, Brazil, Canada, Panama, Puerto Rico, Uruguay and U.S. Virgin Islands, however, will be using men in their late 20s and 30s at the international tournament, July 25-29, in Rio de Janeiro, Brazil.

Suffice it to say, U.S. Pan Am hopefuls – including Kansas University’s Mario Chalmers and Sherron Collins – could help their cause at this week’s tryouts in Philadelphia by convincing the selection committee they have bodies able to survive highly physical play.

Sophomore point guard Collins, at 5-foot-11, 202 pounds, has rippled muscles and a pit-bull mentality.

Junior combo guard Chalmers, who is not known for his bulk, has added five pounds or so of muscle from a year ago and now stands 6-1, 196.

“My shot is coming back a little bit. I’ve been trying to get adjusted to the additional weight I’ve put on,” said Chalmers. He and Collins will be joined by 30 other Pan Am hopefuls today through Saturday at Haverford College, with the squad set to be announced Sunday.

“I am at the size I want to be. I want to get comfortable with this and keep the same weight all season,” Chalmers added.