The Angels released Walker on Sunday, Jeff Fletcher of The Orange County Register reports.
After being cut by the Phillies in April, Walker inked a minor-league deal with the Halos on May 25. Walker proceeded to turn in a 2.45 ERA, 1.36 WHIP and 9:4 K:BB across 11 innings between two appearances in the rookie-level Arizona Complex League and one at Triple-A Salt Lake, but since a promotion to the big leagues wasn't imminent, the veteran right-hander elected to exercise an opt-out clause in his contract. He'll now assess his options as a free agent but will most likely have to settle for another minor-league deal.