After Monday night's 3-0 victory over the Brewers, the reliever shook hands with teammates, cleaned out his locker and exited the clubhouse with a D-backs duffel bag and a large cardboard box of belongings.
Although no roster move has been announced by the organization, Heilman's release could be the move associated with starting pitcher Barry Enright's expected callup. Gibson said on Friday that Enright would be summoned from Triple-A Reno for Tuesday's start against the Brewers.
Heilman re-signed with the D-backs on a one-year, $2 million deal in the offseason.
After he was unable to win a rotation spot out of Spring Training, the right-hander struggled out of the bullpen, posting a 6.88 ERA in 32 games. He struck out 33 batters in 35 1/3 innings and allowed opponents a .318 batting average.
The 32-year-old had a 4.50 ERA with six saves in 70 games for the D-backs in 2010.
Anthony Fenech is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.