Walker started the season with a pair of dazzling starts at Class A Advanced High Desert and Double-A Jackson. He combined to throw 9 1/3 innings, while fanning 17 batters and allowing just one earned run.
But Walker's ERA was 5.82 in five starts with Tacoma.
Jackson Alexander is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.