Major League Baseball has suspended A.J. Preller for 30 days without pay after an investigation into the Drew Pomeranz trade between the San Diego Padres and Boston Red Sox.

Major League Baseball said it was looking into San Diego's handling of medical information of players they were trading. The league's investigators interviewed officials from both teams and then submitted their findings to Rob Manfred.

The matter is now considered closed.

Padres officials instructed their organization's athletic trainers to maintain two distinct files of medical information on their players: one for industry consumption and the other for internal use, according to sources.

Trainers were told in meetings during spring training that the distinction was meant to better position the team for trades.

"I accept full responsibility for issues related to the oversight of our medical administration and record keeping," Preller said in a statement. "I want to emphasize that there was no malicious intent on the part of me, or anyone on my staff, to conceal information or disregard MLB's recommended guidelines. This has been a learning process for me. I will serve my punishment and look forward to being back on the job in 30 days."