PEORIA, Ariz. -- Brian Carlin, the agent for infielder Todd Walker, said in a statement on Tuesday the Major League Baseball Players Association is looking into the Padres' decision to release the 33-year-old veteran.

"The union is looking into the release," Carlin said, "and has serious questions about the Padres' motives. Union representatives have assured us they will do everything necessary to protect and vindicate Todd's rights."

On Monday, the Padres requested unconditional waivers on Walker, effective Tuesday. They did so while insisting the move was strictly a baseball decision and had nothing to do with the $3.95 million arbitration award Walker won last month.

By releasing Walker before March 28, the Padres were only on the hook for termination pay, which equaled $987,500.

"Todd and his family are very disappointed that he was released by the Padres," Carlin went on to say in the statement. "He is looking forward to signing with another team and trying to win a championship."

Walker was hitting .225 this spring, and the Padres said he essentially became expendable with the two other left-handed-hitting reserve infielders on the roster in Russell Branyan and Geoff Blum expected to make the Opening Day roster.

"We said all along that when we break for San Diego we want to break with guys who we think will be the best 25 guys to help his ballclub win," San Diego general manger Kevin Towers said Monday. "Did we look at Spring Training results? Absolutely. That played into our evaluation. We felt there were better fits on our club than [Walker]."