The Baltimore Orioles' slump has crept into a place they least expected to find it -- Don Aase's right arm.

Brought in to protect a one-run lead in the eighth inning tonight, Aase allowed his first runs in three weeks, then two more for good measure and the Detroit Tigers completed a four-game sweep with a 7-5 victory before 38,422 at Memorial Stadium.

So, the 35-29 Orioles will fly to Boston Friday morning with nine losses in their last 11 games, having dropped all the way to eight games behind the first-place Red Sox in the American League East.

Aase (2-2) was going for his 19th save when he walked into a 4-3 lead in the top of the eighth inning, thanks to Tom O'Malley's seventh-inning homer.

Two innings later, Aase was left with his worst performance of the season, having allowed four hits and four runs, the biggest blows coming on Darrell Evans' two-run pinch single and Lou Whitaker's two-run homer.

Good pitcher, bad timing.

"As far as me having a bad appearance, I don't care," Aase said. "It's just that this came at a bad time for the team. We needed better than this going into the Boston series and all."

Aase wasted no time getting into trouble, walking Kirk Gibson in the eighth with one out. He then struck out Lance Parrish for the second out, but Chet Lemon doubled to right to put runners on second and third.

That's when Evans lined a single to right to score two runs and help the Tigers to their first sweep at Memorial Stadium since September 1962.

The Tigers got two more runs in the top of the ninth when Dave Collins singled and scored on Whitaker's eighth homer.

"I got a couple of fastballs up in the eighth," Aase said. "The one Whitaker hit wasn't a good pitch. It wasn't up and it wasn't outside. I haven't been getting my breaking ball over, so he was looking for a fastball."

In all, the Tigers got 10 hits off four Orioles pitchers. Tigers starter Jack Morris (6-4) got the victory as he allowed the Orioles eight hits, leaving after Jim Dwyer's leadoff pinch homer in the ninth. Willie Hernandez got the final three outs for his 12th save.

A complicated situation for the Orioles became a little more complicated in the ninth when designated hitter Larry Sheets fouled a ball off his right instep and twisted his right knee. He had to leave the game.

That left Weaver short one more player, or working with a 22-man roster. He's already without center fielder Fred Lynn, who has a sore ankle, and if Sheets can't play Friday in Boston, the Orioles will consider calling up an outfielder (Ken Gerhart or Jim Traber) from Rochester.

Baltimore starter Mike Flanagan, making his first appearance in three weeks, pitched decently, allowing five hits and three runs in five-plus innings. What he didn't do is win, which is an old refrain for him.

His only victory of the season came April 17. He has made nine starts since then, usually pitching better than a man with a 1-4 record.

The Tigers got a 2-0 lead in the second inning, although only one ball was hit hard. Lance Parrish drew a leadoff walk and, after Lemon and Tom Brookens grounded out, Larry Herndon blooped a double to right for a run.

Dave Engle followed with a double to left to score Herndon and Dave Collins popped up to end the inning.

The Orioles got three runs and a 3-2 lead off Morris in the last of the second. Eddie Murray led off with a single to right and Cal Ripken doubled off the wall in left.

Murray stopped at third on Ripken's hit, but both he and Ripken scored on Sheets' single to left. Sheets went to second on Alan Trammell's error and to third on Al Pardo's single. Sheets scored when Juan Bonilla hit into a double play.

After the second inning, the Orioles didn't get another runner as far as second base until the seventh, when O'Malley homered.

Meanwhile, Flanagan sailed through the third, fourth and fifth innings. In the sixth, Trammell tagged him for a leadoff game-tying homer.

When Flanagan followed the homer by hitting Gibson with a pitch, Weaver brought in reliever Rich Bordi to protect a 3-3 tie.

"He looked good," Weaver said of Flanagan. "It's tough to keep saying, but the bloop hits hurt him. He had surprisingly good control for as long as he was out."

Bordi got the Tigers in order in the sixth, then got the leadoff man in the seventh before walking Engle and allowing Collins a single to left.

Weaver wasted no time going for left-hander Brad Havens to face left-hand-hitting Whitaker, who hit into a double play to end the seventh with the game still tied at 3.

O'Malley's first homer of the season and the ninth of his major league career gave the Orioles a 4-3 lead in the last of the seventh, but it was brief.

Weaver brought in Aase to open the eighth, and the star reliever was on his way to his first loss since April 23.

"It's all over if what happened 18 times before happens again," Weaver said. "But this had to happen sooner or later. No one has ever gone through a season and been perfect. Maybe Hernandez did in 1984, but I don't know anyone else."

Weaver gave second baseman Alan Wiggins the night off, after Wiggins had criticized the fans for booing him when he made three errors Wednesday. Wiggins will return to the lineup sometime this weekend in Boston. Wiggins also asked for and got a brief meeting with General Manager Hank Peters and, later, with Weaver, to discuss his outburst . . .

Tonight's game was the 11th straight in which the Orioles' opposition has scored first . . . Ripken's second-inning double extended his hitting streak to 15 games. He has raised his batting average from .242 to .276 since it began . . . The Orioles have gone 23 games without a starter going the distance, this from the staff that compiled 48 complete games in 1984.