SEATTLE – Coming off a stellar effort for Double-A Jackson, Mariners top pitching prospect Taijuan Walker was promoted to AAA Tacoma on Friday. He will make his Pacific Coast League debut on Tuesday at Cheney Stadium against Fresno, the top affiliate of the Giants. “The plan was to get him to Triple-A at some point this year,” Mariners general manager Jack Zduriencik said. “He’s pitched very well, and I think everyone’s excited about his progression. He had a big night last night. The timing is right.