SEATTLE -- Attempting to do what no Red Sox pitcher has done since Juan Pena on May 8, 1999 -- win his Major League debut -- left-hander Kason Gabbard ultimately came up empty, but through little fault of his own.

Gabbard, who climbed his way from pick No. 872 in the 2000 First-Year Player Draft to Saturday's start at Safeco Field, held his own, scattering eight hits and two earned runs over 5 1/3 innings. The Red Sox, on a day they couldn't get their bats going, were downed by the Mariners and Felix Hernandez, 5-2. Gabbard, the 11th pitcher to start a game for the 2006 Red Sox, took the loss.

The defeat sliced Boston's lead to 2 1/2 games over the Yankees in the American League East.

"I thought he did a very good job," Red Sox manager Terry Francona said of Gabbard. "He was poised; he made a lot of pitches. I was very impressed. I'm telling you, I think this kid can pitch a little bit. He sunk his fastball, he threw his breaking ball and changeup over the plate, he held runners."

The Red Sox simply couldn't get enough runners, generating just four hits against Hernandez over seven innings. Boston also went hitless over the final two frames against the Seattle bullpen, meaning that, one day after clubbing five homers, the Sox fell one short of five hits in this one.

Mike Lowell was one of the few Boston players to connect against Hernandez, roping a solo shot to left to make it 1-0 in the top of the second, the only lead the visitors would hold all day.

"He throws hard," said Lowell. "First of all, [it's] the way his ball runs. Most guys who are at 97 [mph], it doesn't really run. It doesn't have time to run. But he has a good slider, good curveball; he's pretty polished for a 20-year-old. That's impressive. He's got the potential to be a tremendous pitcher."

Gabbard had to be at his best to match Seattle's phenom, and he was.

"I proved that I could pitch up here," said Gabbard, who filled the rotation slot vacated by the ailing Tim Wakefield. "It's still the same game at each level. When you get behind hitters, you've got to make good pitches."

But it all started to unravel in the bottom of the sixth, when a couple of unfortunate events for Boston enabled Seattle to snap a 2-2 tie and go in front for good.

It was all set in motion when Lowell charged a slow roller by Eduardo Perez and made a barehand snag and throw to first. Perez was ruled safe, as first-base umpire Larry Poncino ruled that David Ortiz's foot was off the bag. Several television replays appeared to show Ortiz's foot resting on the bag when the ball landed in his glove.

"[Poncino] said he came off a couple of inches. I didn't see it that way," Francona said. "That's just the way it goes. I told Larry that ... 'those types of plays, when you go back and look at it on the replay, the guy usually stays on longer than you think.' I said, 'I bet you that's the case.' "

Lowell was similarly surprised.

"I didn't really have a good angle. It just seemed like it was called a little late," said Lowell. "David didn't really look like he stretched all that much. It just caught me by surprise because I thought it was more routine than that, but I haven't seen a replay."

Carl Everett followed with a single up the middle, and Gabbard exited in favor of Julian Tavarez. That was when defensive star Alex Gonzalez made a rare gaffe, fielding a chopper and rushing a flip to third base, only to have his throw hit Perez. The ball rolled away, and the error allowed Perez to score the go-ahead run.

It was a tough-luck error for Gonzalez, who made the correct play, but had a tough angle to work with.

"It was the only play I had to make," Gonzalez said. "The only play, I think, for me was at third base, but the runner never slid and I hit him in the back."

The Mariners pushed two more runs across against Tavarez (1 2/3 innings, two hits, two runs, three walks, no strikeouts) in the seventh on a two-run single by Perez, a hit that was set up by two walks and a bloop single by Adrian Beltre that fell in between Gonzalez and Coco Crisp.

Crisp seemed to get a bad jump on the ball, and Gonzalez, stationed at double-play depth, couldn't get back in time to haul it in.

According to Gonzalez, neither player called for the ball.

Though the Lowell blast gave the Red Sox a lead, it didn't last long. The Mariners rallied in their half of the inning. Gabbard issued a pair of walks and an infield hit, loading the bases with two outs. Ichiro Suzuki, surely a better bat handler than anyone Gabbard has ever encountered, golfed a two-run single up the middle to put the Mariners in front.

"It was a good sinker down, and he's a great hitter," Gabbard said. "[He] just put the barrel on the ball, and he got a hit."

But Boston tied it up in the top of the third, with Crisp stealing second and scoring on Ortiz's two-out single to center. That was the end of the offense for the Red Sox, who generated just one hit -- a single by Trot Nixon -- over the final six innings.

It was the first time the Red Sox had seen Hernandez live, and they got a pretty good indication of what all the buzz is about.

"He's got an overpowering fastball," Francona said, "and he threw his breaking ball over the plate in some counts where, again, when you've got velocity [of] 96-97 [mph] and you've got something to go with it, it can make you dominant."

Then there was Gabbard, who took his own measure of pride in holding his own in a pitchers' duel.

"Earlier in my career, it was tough because I had four surgeries, and, I think, after being healthy the last three years, it's been up and down," Gabbard said. "This year, I've just been real consistent with my fastball, and, luckily, I got moved up to Triple-A, and then finally here."