SEATTLE (AP) Struggling starter Taijuan Walker has been optioned to the minors by the Seattle Mariners in a move the club hopes will jump start his sluggish performances on the mound.

The Mariners made the surprising move Monday to open a spot on the 25-man roster for recently acquired reliever Arquimedes Caminero.

Walker made his first start in a month last Saturday but allowed six runs in four innings against the Angels. Walker missed most of July because of tendinitis in his right foot and made only one rehab start in the minors before rejoining the Mariners. He is 4-7 with a 4.10 ERA.

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Seattle manager Scott Servais said the club is sending a message to Walker with the move, saying that with the Mariners in the wild card chase they need more consistency from the young right-hander. Servais said Ariel Miranda will take Walker's spot in the rotation and pitch this weekend in Oakland.