Red Sox general manager Theo Epstein says that pitcher Daisuke Matsuzaka's back issue isn't serious. The right-hander is believed to have a mild back strain. His throwing program will be delayed, but not seriously altered. "His attitude has been great. He was very accepting when we told him we want to treat it conservatively," Epstein said, as relayed by WEEI.com. "I know he's worked really hard this winter to make up for last year and come out and have a big season. That's what we're all hoping for him. We want to slow this thing down so we don't turn something small into something big. Last year, he never really was able to get into condition to pitch in part because of the way things went early in spring. We want to make sure we avoid a repeat of that."