Indianapolis Colts quarterback Andrew Luck threw a football during position drills in June 2018 - the first time he had done so in front of reporters since the team shut him down in October 2017 as he tried to work his way back from a 2015 shoulder injury. But during his summer practice, Luck was chucking a college football - not an NFL one.That's because college footballs are typically smaller than NFL ones, so it put less stress on Luck's surgically repaired shoulder.