I'm guessing he started several games with a low pitch count setting and pitched an inning or two, perhaps when he was under 100% (even well under) and gave up run/s from which his team never came back. That would earn him a loss. In other games his pitch count was boosted, he went 5+ innings and the team won. In 38 other games he didn't have a decision. It would best be answered by looking at his entire season's game log.