BOSTON -- Major League Baseball commissioner Rob Manfred said the Red Sox were given the opportunity to rescind the Drew Pomeranz trade.

The Red Sox opted to keep Pomeranz.

Boston acquired Pomeranz from the Padres on July 14 for top pitching prospect Anderson Espinoza

Major League Baseball suspended Padres GM A.J. Preller on Sept. 15 because it found out Preller instructed the Padres medical staff to create two separate medical files for players, one available to the league and one available for only the team, according to an ESPN.com report. It was a practice meant to hide any medical information from future trade partners.

The Padres hid information about Pomeranz who said the soreness just came on recently.

"It's important to understand that for a very, very long time, there has been a rule in baseball that if something happens in terms of lack of complete information or disclosure with respect to the trade, that the remedy is to rescind the trade," MLB commissioner Rob Manfred said. "You saw that baseball rule operate unfortunately again with the Padres and their trade with the Marlins. We offered early on the Red Sox the opportunity to seek rescission of the trade. And for good baseball reasons -- the biggest one being we were past the trading deadline -- they elected not to seek rescission.

"Once that happens, the rule in baseball has always been that we do not reconfigure trades," Manfred added. "And why is that? Every institution even the commissioner's office ... has limitations. And to figure out once a player is moved, begun playing for another franchise, his physical situation may evolve. Figuring out exactly what happened when is extraordinary difficult if not impossible. Even if you can figure that out, we are not institutionally capable of deciding who would have traded what for what. Even in retrospect. It's just not something the institution can't do. That's why we have the recession rule in the first place."

Manfred said he feels Preller's punishment was harsh enough.

"I felt that Mr. Preller behaved inappropriately in the situation," Manfred said. "He behaved inappropriately to the detriment of two clubs. And I thought that a publicly announced suspension of 30 days, which was the longest suspension of a front office person in 70 years, was a firm statement of our view on how he had behaved or in this case, misbehaved.

"The decision with respect to Mr. Preller's future I do believe is one that the Padres should be allowed to make at the end of the day," Manfred added. "But losing you your general manager for 30 days at this point in the calendar does pretty serious damage not only to the individual but to team as well."