Longtime and well-respected head athletic trainer Ron Porterfield is leaving the Rays for a higher-level job with the Dodgers, the Tampa Bay Times has learned.Porterfield, 52, has been the Rays top trainer for 12 seasons and with the organization for 21 years, signing on during the 1996 franchise formation and working his way up from minor-league coordinator.The Rays are expected to promote from within to replace Porterfield, with candidates including assistants Paul Harker and Mark Vinson, and minor-league training coordinator Joe Benge.Porterfield will serve as medical director with the Dodgers, working under former Rays baseball operations chief Andrew Friedman, to provide leadership, oversight and direction to their staff while based at the team's Arizona facility."It wan an extremely difficult decision," Porterfield said Friday. "I want to make clear how much the Rays organization means to me, and the people from the top to the bottom. They made me want to go to work.It's been my home for 21 years."Porterfield said he decided to make the move for several reasons: That he was moving into a newly created position to provide leadership, that it would create opportunity for promotion among the Rays staff and that it would allow him to spend more time with his family on a daily basis, and to be closer to extended family, including his parents, in New Mexico."It's a new chapter for me," Porterfield said.Under Porterfield, the Rays were considered to have one of the top training staffs in the game. Selection to work the 2013 All-Star Game, and a 2009 PBATS Medical Staff of the Year award were among several industry honors during his tenure.