DETROIT, SEPT. 30 -- On the last day of September, with temperatures dipping into the 40s and the pungent smell of Italian sausage drifting through Tiger Stadium, Sparky Anderson gambled on a Dan Petry comeback.

It was chilly evenings like this in 1984 when Petry helped the Tigers win a World Series and completed a season as one of the most respected right-handed pitchers in baseball. Since then, his career has taken a rapid downward spiral, with an elbow operation last season, two complete games in his last 41 starts and, most recently, a demotion to the bullpen.

Tonight, when the Tigers desperately needed something special from him, they got nothing. A last-minute replacement for injured Walt Terrell, Petry was around for only 2 1/3 innings and hammered for five runs in the Tigers' 7-3 loss to Baltimore before 19,434.

Orioles rookie Jose Mesa, 21, made his fifth major league start his best one, allowing seven hits in 8 2/3 inning to win for the first time. He allowed base runners in all but the first and eighth innings, but had a 92 mph fastball and enough of a change-up to keep the Tigers off balance.

In baseball's closest divisional race in five years, the Tigers and Blue Jays have both slipped on unexpected ice. While the Blue Jays have lost three straight to a respectable Milwaukee team, Detroit has lost two of three to an Orioles team that has been unable to beat much of anyone.

Thanks to Toronto's 5-2 loss to Milwaukee tonight, the Tigers remained 1 1/2 games out of first place. Still, the Detroit loss reduces the Blue Jays' magic number to three.

So, while the Blue Jays (96-63) are off Thursday, the Orioles and Tigers (94-64) play the fourth game of this series. If the Tigers win Thursday, they will have to beat the Blue Jays twice this weekend to force a one-game playoff Monday at Tiger Stadium. If they lose, they can win the division outright only by sweeping the Blue Jays.

"We ought to give Milwaukee a share of our money if we win it," said Anderson, the Tigers' manager. "Those three games Toronto lost are just like wins for us. Who would have dreamed that would happen? We're so lucky because we should be eliminated by now. The way things are going we might fall into this thing yet. . . . Luck sure plays a part in things, but I hope we don't try to ride it all the way."

Life would have been simpler for the Tigers tonight had Petry (9-7) been sharp. Instead, he was nothing close to the Petry of the early '80s -- 67 victories from 1982 through 1985 -- allowing a run in the first, three in the second and another in the third as the Orioles (66-92) won for only the third time in their last 22 games.

The Orioles collected only seven hits in all, but three of them were home runs by Terry Kennedy, Fred Lynn and Cal Ripken Jr.

Petry hit leadoff man Pete Stanicek with a pitch in the first inning. Stanicek stole second, went to third on a Jim Dwyer flyout and scored on a grounder by Lynn for a 1-0 lead.

In the second, Larry Sheets and Ray Knight got one-out singles, and Kennedy homered into the upper-deck in right field for a 4-0 lead. It was Kennedy's 18th this season, but only his fifth in 72 games.

Lynn led off the third with his 23rd homer to make it 5-0, and when Murray hit a 420-foot fly ball to center that Chet Lemon caught, Petry was gone.

"I never gave the team a chance," Petry said. "We were behind, 4-0, after the second inning, and most teams are not going to blow that. . . . I just didn't have much."

The Orioles scored their last two runs off reliever Eric King in the fifth. Lynn walked, Eddie Murray was safe on a fielder's choice grounder and Ripken homered.

Meanwhile, Mesa (1-3) needed a workhorse 150 pitches and was helped considerably by the quick runs and three double plays.

The Tigers scored in the fourth when rookie Jim Walewander drew a leadoff walk and eventually came home on Kirk Gibson's groundout. Their final two runs came on Darrell Evans' 34th homer and Lemon's 20th. Those were the 221st and 222nd allowed by the Orioles this season, a major league record.

Still, on a team desperate for pitching, Mesa has become a brightly shining star.

"I really enjoyed myself tonight," Mesa said. "I had a good fastball and stayed with it. I wasn't tired. I think I could have finished."

Catcher Kennedy was impressed again, saying, "Just when I thought he was losing it, he threw some great pitches to Gibson {in the eighth}. He'd lost some pop for a couple of innings before that, but he really got it back. He's still just a puppy, but you really have to be excited about him."

Orioles Notes:

Reliever Mike Kinnunen has made 47 appearances over parts of three seasons and has yet to get a victory, loss or a save . . . Anderson said he plans to start Terrell Thursday, although the pitcher's neck was still very sore tonight.