By Madison Williams Dallas already has lost two defensive backs to season-ending injuries this year. Cowboys safety Jayron Kearse was helped off the field Sunday during pregame warm-ups, per Jori Epstein of Yahoo! Sports. Shortly afterward, Kearse returned to the field with a limp and performed leg stretches. The safety was listed as questionable with a left knee injury before Dallas’s matchup against the Texans, per KristiCowboy. Kearse landed awkwardly on his left leg during a drill with the defensive backs. He was then helped to the tunnel by Cowboys two staff members. Despite the injury, K…