The Cowboys suffered another set back at center when second year player Bill Nagy went down with what is believed to be a high ankle sprain on Monday. He underwent a magnetic resonance imaging exam on Tuesday. The Cowboys have yet to receive the results of the exam but injury is a disappointment to Nagy who was sidelined last season after fracturing the same left ankle and the Cowboys, who had hoped he could challenge Phil Costa for the starting job along with Kevin Kowalski. But Kowalski is already on the physically unable to perform list with an ankle injury. The Cowboys gave guard David Arkin some snaps at center on Tuesday. Arkin had a less than impressive debut with several botched snaps.