The irony was incredible, as was the performance.

Doyle Alexander, a former New York Yankee, today won his 17th game in what happened to be the most important game in the nine-year history of the Toronto Blue Jays. Alexander gave up only five hits and one run to the most productive team in the American League as the Blue Jays beat the Yankees, 5-1, to clinch their first AL East Division title.

Toronto will meet the Kansas City Royals in the league championship series, which opens Tuesday in Toronto.

After he retired Ron Hassey on the last of his 18 fly-ball outs, Alexander was carried from the field atop the shoulders of his teammates, while 44,608 fans cheered. Before he ducked into the dugout, he gave the crowd a thumbs-up sign.

"I loved it, I loved it," he said.

Alexander was released in 1983 by the Yankees, then was signed by the Blue Jays to a minor league contract.

"It doesn't matter who it was, as long as we won," Alexander said in the Blue Jays' clubhouse, champagne dripping off the end of his nose. "I pitched the pennant-clincher for the Yankees in 1976. It's been a long time since I've been there, and it feels pretty good."

The Blue Jays had dropped four straight, including Friday night's 4-3 ninth-inning loss to the Yankees, which they hadn't done since the All-Star break. But their confidence never waned. The sign hanging in the clubhouse said it all: "This team was counted out several times by many people, but we did not hear the bell."

Amid the celebration, Blue Jays Manager Bobby Cox said he had had confidence in Alexander, although "with the wind blowing straight to right and all the left handers the Yankees have, you never know."

The temperature was 54 degrees at game time, with wind gusts (blowing toward right field) between 19 and 25 mph. The Blue Jays got their first three runs on home runs to right field.

"You saw what a couple mistakes did with left-handed hitters," Alexander said of homers by teammates Ernie Whitt, Lloyd Moseby and Willie Upshaw. "I was trying to keep the ball away from them and let them hit it to left. The thing was, I didn't want to walk people and give them a chance to even it with one swing of the bat."

Alexander did not walk a man.

Yankees starter Joe Cowley was in trouble in the first, when Moseby reached third, but Cowley got out of it.

He wasn't so lucky in the second. Whitt, the Blue Jays' catcher, was in the No. 7 spot in the order -- and for good reason. Whitt was hitting .245 and had only three hits in his last 27 at bats. With two out, Cowley let a 1-2 count on Whitt slip to 3-2. Cowley's next mistake was a low fast ball over the plate that Whitt got up into the wind and over the right-center field fence for his 19th homer of the year and a 1-0 lead.

"We've been struggling with the bat," Whitt said. "Finally we broke loose and scored runs for our pitchers. It's a tremendous feeling. That 99th win was a tough one, but we finally got it today."

Cowley started strongly in the third, getting Damaso Garcia to bounce out to Willie Randolph at second. But that was it.

Moseby worked the count to 3-2 and then crushed Cowley's next offering. It was Moseby's 18th home run of the year, the same number he has had in each of the last two seasons.

"I was glad to redeem myself," said Moseby, whose error Firday night allowed the Yankees to score their winning run. Then, reacting to the yell of a teammate, Moseby rushed off saying, "I got Reagan on the phone, I got Reagan on the phone." President Reagan did not call, but then, it didn't really matter. There's always the World Series.

Yankees Manager Billy Martin gave Cowley one more shot, and that's exactly what Upshaw delivered. Cowley hung a 1-2 curve ball over the middle of the plate, and Upshaw sent a line drive out for his 15th home run of the year.

The Blue Jays weren't finished, though. Designated hitter Al Oliver greeted reliever Bob Shirley with a double into the right-field corner. Garth Iorg pinch hit for Rance Mulliniks, and Iorg's one-hop grounder came up near the face of Shirley, who knocked the ball down with his bare left hand. Iorg was safe at first, Oliver was safe at third, and Shirley was out of the game, though it was determined that he had only a bruise.

Rich Bordi, the third Yankees pitcher, got all the time he needed to warm up because of Shirley's injury, but he couldn't prevent the Blue Jays from scoring again. George Bell's sacrifice fly to center field scored Oliver from third for a 4-0 lead.

Meanwhile, Alexander gave up only one hit -- Don Baylor's single in the second -- while shutting out the Yankees in the first three innings.

The Yankees, who have more runs (804) than any other team in the league this year, finally got one in the fourth, but should have had more. Ken Griffey led off by doubling into the right field corner. Don Mattingly, who was 0 for 5 Friday night, was robbed of probably a double. Upshaw dived to stop a two-bouncer and threw to Alexander covering. Griffey moved to third and scored on Dave Winfield's single to center.

Tony Fernandez doubled and scored in the fourth to make it 5-1, but it really didn't matter.