Complex sentence: Lockhart played for the Cowboys during a low point in the franchise history, and a lot of times he was one of the few legitimate players on sub par teams, which eventually ended up costing him a chance to earn Pro Bowl honors and other accolades.
Split into simpler sentences: Lockhart played for the Cowboys during a low point in the franchise's history. He was one of the few standout players on otherwise lackluster teams, which eventually cost him a chance to earn Pro Bowl honors and other accolades.