Texans coach Bill O’Brien recently credited backup quarterback Ryan Mallett with putting in noticeable extra work. Mallett acknowledged he’s been spending extra time at NRG Stadium. But he joked that he wasn’t going to divulge his “office hours,” adding that his extra effort is just part of his job. “I do what I’ve always done, man, is work my (butt) off and try and get better everyday,” Mallett said Thursday at NRG Stadium.