Japanese ace pitcher Yu Darvish will not take the mound for the Texas Rangers' season opener next Monday because of a stiff neck, the Major League Baseball club announced Tuesday. The Rangers pulled Darvish from a pre-season training start last Friday because of his sore neck and the injury still bothered him on Monday, when the team decided to send him for more medical tests. "If I felt right, I would continue to throw," Darvish said. "But I didn't, so I stopped throwing." The Rangers have not announced who will replace Darvish as their opening-day pitcher against visiting Philadelphia. Darvish says that the problem came because he slept in a bad position one night last week, but the team is concerned there might me more to it than that. "He has not shown the progress that we would like," Rangers assistant general manager Thad Levine said. "We want to start ruling out things at this point. At this stage we're open to it being more than just sleeping wrong." The 27-year-old right-hander went 13-9 with a 2.83 earned-run average in 32 starts last year and in 2012, his first season since coming to the Rangers from Japan, he was 16-9 with a 3.90 earned-run average. Source: AFP