Oakland Raiders linebacker Khalil Mack (52) stretches during their training camp practice in Napa, Calif., on Friday, July 25, 2014. Temperatures were
Oakland Raiders linebacker Khalil Mack (52) stretches during their training camp practice in Napa, Calif., on Friday, July 25, 2014. Temperatures were nearly 100 degrees during the first practice of the summer at the Raiders training site in Napa. (Jane Tyska/Bay Area News Group)