Morrow has made four starts with Tacoma, including a 4 2/3-inning outing Thursday at Portland when he struck out 10, and is scheduled to pitch again Tuesday.

"The next one after that would be the 31st, which means you'd have to make a roster move if we brought him up then," Riggleman said. "If you wait one more day (when rosters expand), you don't have to make a roster move. Whether he gets that other performance down there or up here remains to be determined, but I don't think we'll see him here before (Sept. 1)."

While the Mariners don't want to rush Morrow, who went 1-2 with a 1.47 ERA and 10 saves in 40 relief appearances, they'd like to get a good look at him as they consider their options for the 2009 starting rotation.

Even if he starts two more times with Tacoma, Morrow would get five starts in September with the Mariners.

MARINERS 7, A's 5: Catcher Jeff Clement continued his late hitting surge, doubling twice and driving home three runs Friday. His two-run double capped a four-run fourth inning and his RBI double helped the Mariners score twice in the seventh, when they broke a 5-5 tie. Clement, a left-handed hitter, is batting .227 for the season and, against left-handed pitching, has a .289 average with five of his 20 RBIs.