Back on Opening Day, it was easy for the Baltimore Orioles to imagine the season's final week as being tinged with pennant-race atmosphere, with six head-to-head games against their top division rivals. They were half-right.

While the New York Yankees came here this week intent on clinching the American League East title, the Orioles are playing out their disappointing season with a shell of their original roster. Even their young players appear tired.

In a 9-5 loss to the Yankees tonight in front of 44,711 at Oriole Park at Camden Yards -- a large portion of whom stood cheering as Yankees closer Mariano Rivera threw the final pitch -- the Orioles showed how far they have come from the optimism and veteran-heavy look of Opening Day, and how far behind the Yankees they remain.

The Orioles' lineup tonight featured only three players -- shortstop Mike Bordick, left fielder B.J. Surhoff and catcher Charles Johnson -- who were in the same positions the first game of the season. The rest, via attrition or injury, were rookies and subs pressed into action. Three of them -- center fielder Eugene Kingsale, second baseman Jerry Hairston and first baseman Jeff Conine -- could be at those positions next Opening Day.

At the same time, the Orioles' pitching staff, which long ago righted itself to become the dependable force it always was supposed to be, regressed tonight with one of its more unseemly performances of the season. Five pitchers combined to walk 11 Yankees. Rookie left-hander B.J. Ryan walked the bases loaded in the seventh inning; rookie right-hander Gabe Molina nearly duplicated the feat in the eighth.

The Yankees' victory reduced their magic number for clinching the AL East to two.

"The Yankees make you throw it over the plate, and we didn't do it," said Orioles Manager Ray Miller. "They don't swing at balls."

Orioles starter Sidney Ponson, their 22-year-old right-hander, continued his late-season swoon, giving up four walks and seven earned runs in 5 2/3 innings. Ponson (12-12), who at one point this season had a 10-5 record, is 1-5 with a 7.01 earned run average in his last nine starts. Miller attributes Ponson's decline to the toll of his first full major league season, and the extra weight Ponson packs on his 6-foot-1 frame, the dangers of which were evident in the downfall of another husky former Oriole, cast-off pitcher Rocky Coppinger.

"You can't cut any corners if you're going to perform here," Miller said. "You have to be 100 percent in shape. If he's willing to make that 100-percent devotion to it, he has a chance to be a number-one pitcher. Or he can choose the Rocky Coppinger way. Not a good way to go."

The Orioles staked Ponson to a 4-1 lead on a two-run double by designated hitter Albert Belle in the first inning and a two-run single by Bordick in the second. But the lead was gone by the third, when Yankees first baseman Tino Martinez hit a three-run homer off Ponson into the bleachers in right-center to tie the game.

It was the 35th homer given up this season by Ponson, tying the club record set by Robin Roberts in 1963 and equaled by Scott McGregor in 1986.

Orioles rookie third baseman Ryan Minor, again hoping to prove himself in Cal Ripken's absence, lined a solo homer to left off rookie left-hander Ed Yarnall to give the Orioles back the lead, but again it didn't last.

A lead-off double by Bernie Williams launched a three-run sixth inning that ended Ponson's night. The key play was a weak dribbler down the third-base line by Ricky Ledee, which Ponson fielded and threw into the Orioles' dugout.

After the game, Miller revealed he did not have left-hander Doug Johns or right-hander Al Reyes available because of minor injuries, forcing him to stay with Ponson longer than he had hoped. But he also hoped Ponson could have made it through the sixth. "He really tried hard tonight, maybe too hard," Miller said. "That's why you have to be in the best shape of your life in the spring. He's not used to pitching this much. You feel physically okay, but your arms and legs start to tire out, and you just don't throw the ball where you want to."

Orioles Notes: Outfielder Brady Anderson, who is suffering from a strained right quadriceps, was out of the lineup tonight and likely will miss at least another game. . . .

The Orioles signed 17-year-old shortstop Luis Alou, son of Montreal Expos Manager Felipe Alou, to a minor league contract for the 2000 season. Terms were not disclosed.