BALTIMORE, SEPT. 6 -- Jim Dwyer's day had been long and boring, even by his own standards. He sat in the clubhouse during a rained-out batting practice. He sat there some more during two rain delays totaling more than two hours.

Then, a game between the Oakland Athletics and Baltimore Orioles was almost into its fourth hour when someone finally called his name. On a rainy afternoon when the two teams totaled 18 hits and four errors, he was the 32nd and last player to be sent into the Orioles' 7-6 victory.

The deciding one, too. With a teammate on first base and one out in the ninth, he hit Dennis Eckersley's first-pitch fastball into the right-field seats to give the Orioles a victory before a few hundred fans (of what had been an announced crowd of 18,160).

If the Orioles (62-74) don't remember this game, one they led, 4-1, after three innings, then trailed, 6-5, into the ninth, the Athletics certainly will because it cost them a chance to move within two games of first-place the Minnesota Twins in the American League West.

It was also a tough way for Reggie Jackson to end another phase of his career. For his last game in Baltimore, he had been penciled into the lineup, but scratched at the last minute when he still couldn't run because of a sore left hamstring.

He spent the day in the dugout wearing a warmup jacket, leaving only in the sixth to tip his cap after the Orioles saluted him with a Diamond Vision highlight film of his career.

"Thank everyone for me," he said. "They've been great here."

Dwyer wouldn't have batted, either, if things had gone as planned for the Orioles. Cal Ripken Jr.'s 24th homer had gotten them within 6-5 in the eighth, and the ninth opened with Mike Young singling to right.

Orioles Manager Cal Ripken Sr. then wanted Mike Hart to sacrifice. Hart bunted right to third baseman Carney Lansford, who threw to second for a force. Had Hart gotten Young to second, Ripken was going to send up Fred Lynn to bat for Rene Gonzales "because Freddie hits a little more for average."

But with the potential tying run on first, Ripken went for the home run, and it got it, Dwyer's career-high 14th. This one came at an important time for a lot of reasons. One is that, at 37 Dwyer still wants to prove he deserves a contract for 1988. It also comes at a time when his playing time has dwindled to almost nothing, especially with rookie Pete Stanicek taking over as designated hitter.

Rookie Mark McGwire's 42nd homer got the A's up, 1-0, in the second, but in the bottom of the inning Larry Sheets hit his 27th. For the day, he went three for four with two doubles and the homer.

The Orioles then took a 4-1 lead in the third when a combination of the awful conditions and some flat pitches by Oakland starter Steve Ontiveros got the A's in trouble.

With one out, Hart doubled to right. He took third on an infield grounder by Stanicek, who made his first professional start at third base and committed two errors. Bill Ripken singled to left for a 2-1 lead, and Ontiveros walked Ripken Jr. and designated hitter Eddie Murray to load the bases. Sheets splashed a bloop double to center to score two more runs, and Ontiveros got first baseman Ray Knight on an infield grounder.

It appeared John Habyan would make the lead stand up, as he took a two-hitter into the seventh. But his day changed when Ripken Jr. let Carney Lansford's liner slip between his legs with one out. Dwayne Murphy looped a single to left, and with runners on first and second Ripken Sr. brought in Mark Williamson.

Bad move. McGwire singled to load the bases. Mike Davis singled to score one run, and Williamson walked Terry Steinbach to score another. When Alfredo Griffin blooped a single to center, McGwire's run tied it, 4-4.

Ripken Sr. then brought in Luis DeLeon, just back from Rochester. DeLeon did his job, getting Luis Polonia to hit a hard grounder to first. Knight picked up the ball, and, with plenty of time to get Davis at the plate, threw into the dirt. The ball bounced away from Terry Kennedy, and Davis made it 5-4. Steinbach went to third, and Tony Phillips' sacrifice fly scored Steinbach with the fifth run of the inning.

Ripken Jr.'s 24th home run got the Orioles within 6-5 in the eighth.