SEATTLE — There’s a reason the Seattle Mariners own the Oakland A’s this season — pitching.

It’s also the reason the Mariners have little more than flickering playoff hopes at a time when they hoped to come back to Safeco Field for their most meaningful baseball of the season.

Effective pitching was the key to the Mariners’ 10-3 record over Oakland entering Monday, having held the A’s to 3.2 runs per game. Those games happened at a different, happier time for the Mariners.

The lack of quality pitching again spun the M’s to a 9-3 loss, their 14th defeat in 16 games, when 123 innings of Horacio Ramirez put them in a hole they couldn’t escape.

The A’s scored five runs in the second inning off Ramirez, including Kurt Suzuki’s grand slam. Dan Johnson also hit a grand slam in the ninth off M’s left-hander Ryan Rowland-Smith — set up by right-hander Brandon Morrow, who loaded the bases — to rob the M’s of all hope after they’d come back to trail 5-3.

The loss pushed the Mariners farther into the black hole of the standings, where they’re 812 games from the first-place Angels in the American League West and 512 behind the Yankees for the AL wild card with 20 games remaining.

Ramirez, now 8-6 with a 6.80 ERA, did exactly what the Mariners couldn’t afford — falling behind and forcing manager John McLaren into his bullpen early.

McLaren had no choice.

“They got some people on base and he made a bad pitch,” McLaren said. “If you go back over (Ramirez’s) games, it’s just a pitch here or there. This was the case again.

“I thought the first inning, he came out and really looked great. He was crisp and he went right at the hitters. Then it turned on him pretty quickly.”

Ramirez was 2-0 in three career starts against the A’s, but his 6.48 ERA vs. Oakland caught up with him.

He retired the A’s 1-2-3 in the first inning but gave up two walks and two hits, including Jack Hannahan’s RBI single for a 1-0 A’s lead, then hung a breaking pitch over the middle of the plate with the bases loaded, and Suzuki cleared them.

He drove that pitch into the A’s bullpen beyond the left-field fence for his seventh homer this season and his first grand slam.

Ramirez got the second out of the inning when Shannon Stewart grounded out, but Marco Scutaro followed with a single.

McLaren bolted from the dugout, took the ball from Ramirez and handed it to lefty Ryan Feierabend, who pitched like he should have been on the mound from the beginning.

Feierabend got the final out of the third inning and escaped a bases-loaded jam in the fourth. He held the A’s to four hits and struck out five in 513 scoreless innings.

“I thought Feierabend was tremendous,” McLaren said. “He kept us in the game and we fought back.”

A’s right-hander Joe Blanton held the M’s to four hits through six innings, and the most solid contact they had to that point happened in the fourth when Jose Guillen was hit by a pitch. It was the 18th time this season Guillen had been hit, breaking Dave Valle’s 1993 team record.

The Mariners broke through in the seventh when Ben Broussard singled and Jose Vidro doubled with nobody out, followed by RBI ground outs by Kenji Johjima and Jose Lopez.

Yuniesky Betancourt and Ichiro Suzuki each singled with two outs and Adrian Beltre worked Blanton hard, fouling off six pitches, before hitting a hard one-hopper to Johnson at first base for the final out.

Guillen hit a solo homer in the eighth off A’s left-hander Alan Embree, making the score 5-3, but Johnson’s grand slam in the ninth ended any hope that the Mariners could produce a meaningful rally in their last at-bat.

“It’s easy to get down, but the guys care out there,” McLaren said. “We’re preparing and playing hard every night. We just need to pitch a little better and maybe hit a little better.”

It’s more likely that the Mariners do it without first baseman Richie Sexson. Team physician Dr. Edward Khalfayan examined his ailing left hamstring Monday night and ordered an MRI for today.