Throw in a couple more errors, giving Oakland 18 errors in its past 10 games, and you've got yourself a forgettable night at the old yard.
"We fell behind early and their guy was on top of his game," A's manager Bob Geren said. "That's usually a bad combination."
Mortensen, a 24-year-old making his seventh big league appearance and sixth start, allowed six earned runs on eight hits before exiting with nobody out in the second inning. Ken Griffey Jr.'s three-run homer to center was the biggest blow, and Mortensen also hit a batter and made a throwing error.
Griffey, who has 18 homers this year, 629 in his career and a pair of three-run shots in this series, has gone deep on 407 different pitchers during his Hall of Fame-caliber career. Trevor Cahill was added to the list Tuesday, and Mortensen made it by grooving a 2-0 fastball that Junior jacked to straightaway center.
"You know the name. You know it's him, and when he steps in the batter's box, you're like, 'Oh, now I'm facing Ken Griffey Jr.,'" Mortensen said. "But then you have to push it back in your mind. ... It was a fastball out over the plate, and you can't go there with him on a 2-0 pitch."
Meanwhile, Oakland's offense had no answer for Morrow, who gave up a fourth-inning infield single to Rajai Davis and nothing else -- no walks, no hit batters, no errors -- until the eighth. Morrow tossed eight innings and struck out nine.
Eric Patterson and Travis Buck drew two-out walks in the eighth before Morrow, who hit 97 mph on the radar gun with some frequency, ended his night by retiring Cliff Pennington on a fly ball to right field.
Landon Powell saved the A's from the indignity of not getting a hit into the outfield when he signed with two out in the ninth before Jack Cust struck out to end it.
"Everything he threw was right around the plate," A's first baseman Daric Barton said of Morrow. "He moved the ball around, in and out, made good pitches when he had to. He threw a great game."
Asked if it was the best he's seen Morrow, Geren said, "Yeah, without a doubt."
Six of the first seven Mariners batters in the first inning reached base as the hosts charged to a 4-0 lead. Ichiro Suzuki tripled to open the second and scored on a single by Franklin Gutierrez, who scored on a popup to right field that fell for a double before Mortensen was pulled from his final start of the season.
"I was falling behind in the count, leaving balls up, pretty much everything you don't want to do," said Mortensen, who gave up seven runs -- three earned -- over 4 2/3 innings his previous time out to snap a two-start winning streak. "A lot of things didn't go my way tonight. Nothing did."
Adam Moore hit a two-out homer off A's righty Jeff Gray, but the bullpen provided Oakland's only highlights.
Rookie lefty Brad Kilby was outstanding after taking over for Mortensen, striking out four and stranding runners at the corners in each of his two innings. Righty Jon Meloan followed Gray with two perfect frames, striking out three.
Meloan (five appearances) has not allowed an earned run since joining the A's this month, but perhaps the most encouraging bullpen outing of the evening came from a rookie who brought a 9.00 ERA into the game.
Petrol-pumping righty Henry Rodriguez, he of the 100-mph fastball and oft-questionable command, breezed through the bottom of the seventh on 12 pitches, striking out two. He picked up another strikeout in the eighth.
"Henry hit 101, pumping strikes," Geren said. "That was impressive."