In a surprise move, the Mariners optioned right-hander Taijaun Walker to Triple-A Tacoma on Monday and replaced him with reliever Arquimedes Caminero.
In his first start since being activated off the 15-day disabled list, Walker allowed six runs over four innings Saturday in the Mariners 8-6 win over the Angels at Safeco Field. He had missed a little more than a month with right foot tendinitis. In 2016, Walker is 4-7 with a 4.10 ERA in 16 starts.
Left-hander Ariel Miranda will take Walker's spot in the rotation, per The (Tacoma) News Tribune.
Caminero, 29, was acquired via trade Saturday from the Pittsburgh Pirates in exchange for a player to be named and a conditional player to be named.