Older, but no less sharp of mind, Henry Blanco instantly conjured up the memory of his only other big-league grand slam. That came 13 years ago, before his fellow Mariners catcher and the second baseman he now plays alongside had enjoyed their 10th birthdays. But Blanco, all 41 years, 290 days of him, turned back the clock just long enough Saturday to give the Mariners their only runs in a 4-0 win over the Oakland Athletics. After an extended, in-game dugout hug from eventual winning pitcher Felix Hernandez, plus postgame back pats from his still-in-shock teammates, Blanco was asked whether he recalled the only other time he’d done this with the bases loaded. “I remember it was against Jason Schmidt,’’ he said of the former Pirates staff ace. “I got a fastball to hit, and I hit it out. Obviously, the same thing happened today.’’ Fastballs are about the only pitches Blanco still can drive with frequency these days, given his sporadic playing time prior to signing with the Mariners on Friday. So, when A’s starter A.J. Griffin tried to paint a first-pitch, 88 mph four-seamer on the inside corner with one out and the bases juiced in the sixth, Blanco wasn’t about to wait for something else. “I was looking for a pitch where I could drive in a run,’’ he said. “I got a first pitch and I hit it pretty good.’’ Then, he crossed his fingers as he watched the ball travel down the left-field line, almost willing it to stay fair — knowing the chance probably wouldn’t come around again soon. The ball landed just inside the foul pole and the visiting team’s dugout erupted in celebration. “I was hoping it would stay fair and it did,’’ said Blanco, whose gap between slams was the fifth-longest in major league history. “It was close to the line, so, I didn’t want it to go foul. That was the main thing.’’ The crowd of 24,378 at The Coliseum looked on in shocked silence, realizing the game had likely just been decided in a second straight loss for the home team. Oakland had won 11 in a row at home and was the hottest team in baseball before the Mariners came in here and took the first two of this series to improve to seven games under .500. Hernandez tossed seven scoreless innings to continue a remarkable stretch by his team’s starting rotation. Mariners starters have allowed just two earned runs their last six outings, while throwing eight consecutive “quality starts” of at least six innings pitched, three earned runs or fewer allowed.