The Mariners have called up pitching prospect Taijuan Walker to start Friday at Houston, MLB.com reports. Walker entered the season as the No. 5 prospect in all of baseball, according to MLB.com.
Walker has gone 5-3 with a 3.61 ERA over 11 starts since being promoted to Triple-A Tacoma. He has 64 strikeouts in 57 1/3 innings with Tacoma.