DETROIT — It looked like the 175-pound, emergency-replacement shortstop, who came into the game with just one home run in nearly two years, was going to secure Mariners ace Felix Hernandez a needed win.

Instead, after pounding a tying homer in the sixth and scoring the go-ahead run in the seventh on Tuesday night, reserve shortstop Josh Wilson helped give it all away in the eighth. His crucial error on a routine grounder proved costly in a four-run inning by the Detroit Tigers that resulted in a 5-3 Mariners loss.

The stunning reversal also cost Hernandez a potential win as he tries to keep pace with competitors in the AL Cy Young Award race. Hernandez had left the game with a 3-1 lead, having tossed seven innings of one-run ball and seen Wilson and the offense come through with two runs in the eighth.

But it wasn't enough.

Mark Lowe yielded a leadoff homer to Alex Avila to start the eighth and cut the lead to 3-2. Lowe then allowed a single by Adam Everett, and then — with one out — Placido Polanco hit a grounder toward Wilson.

The ball likely wasn't hit hard enough to turn a double play, but Wilson charged in quickly on it — and had it scoot under his glove.

The crowd of 33,710 at Comerica Park erupted, sensing what was coming next. A rattled-looking Lowe walked Carlos Guillen to load the bases, then gave up a two-run single to Miguel Cabrera that put Detroit ahead to stay.

Detroit went on to score an additional run in the inning on a high throw home during an attempted double-steal gone awry for the Tigers. Fernando Rodney gave up a hit in the ninth, but nailed down the save.

The only run allowed by Hernandez came against a hitter he probably should never have been facing. A few batters earlier, Clete Thomas was leading off and skied a ball into foul territory down the left-field line near the stands.

Mariners left fielder Ryan Langerhans came sliding in on the ball and appeared poised to make a fine catch. But at the last moment, a fan reached out from the stands and snatched the ball away.

Langerhans stared angrily at the glove-wearing fan, who appeared to have blatantly interfered with a ball that would have otherwise landed in play by several feet. Mariners manager Don Wakamatsu sprinted out to argue the noninterference call with third-base umpire Dan Iassonga, to no avail.

The inning continued, Thomas stole second, and with two out, Adam Everett hit a soft liner to center on a 1-2 pitch to give Detroit a 1-0 lead.

Things appeared as if they might stay that way as Tigers starter Rick Porcello steamrollered the Mariners for most of the first five innings. Porcello had allowed only one hit to that point, and 10 of his 69 total pitches had come in a strikeout at-bat by Ichiro in the fourth inning.

Porcello also had to throw five extra pitches after a two-out error in the fifth.

Otherwise, he had brilliant and had notched his career-best eighth strikeout to start the sixth inning. He then appeared headed for whiff No. 9, jumping ahead 1-2 on Wilson before he pounded a pitch over the left-field wall.

It was the second home run in five days for Wilson, who hadn't gone deep since September 2007 before tagging the Yankees' CC Sabathia on a 1-2 pitch at Safeco Field last week.

Porcello never quite recovered from Wilson's game-tying blast, issuing consecutive singles to Ichiro and Russell Branyan before walking Ken Griffey Jr. with two out to load the bases on his 24th pitch of the inning.

Tigers manager Jim Leyland had seen enough and pulled Porcello right there. Ryan Perry came in and got Franklin Gutierrez to fly out to end the threat, then struck out the side in the seventh.

Hernandez did his best to keep pace, retiring 12 of 13 after a leadoff single in the fourth and striking out six during that span.

The Mariners finally gave Hernandez the break he was looking for in the eighth, having scored just one run in support of him the last 14 innings he'd been on the mound. It was Wilson getting things started again, this time chasing Perry by leading off the eighth with a single.

Bobby Seay came on to face Ichiro and yielded a double down the right-field line to put runners at second and third. Branyan promptly delivered the needed deep fly ball to right, bringing Wilson home for a 2-1 lead on the sacrifice fly.

Griffey added another sacrifice fly that inning, and Hernandez appeared poised to improve to 13-4 on the season. But it was not to be.