BOSTON, AUG. 21 -- What Black Monday was to Wall Street, 1990 is becoming to Mickey Tettleton. The salary drive of the Baltimore Orioles' slumping catcher has come to resemble an all-encompassing swing and a miss.

Tettleton will be eligible for free agency after the season, and early indications were he'd have a big payday in store. Tony Pena signed with the Boston Red Sox during the past offseason for $2 million per year, and Tettleton had surpassed Pena's 1989 power numbers -- four home runs and 37 RBI -- by the all-star break.

Tettleton is far from Pena's equal defensively, but he is a rare commodity -- a catcher with clout. A year ago he had 26 homers and 65 RBI in 411 at-bats; he led major league catchers in home runs and he spent just 75 games behind the plate.

But Tettleton has tailed off considerably this season. He started slowly, then seemed to straighten himself out during a five-week stretch in May and June when he hit 11 of his 12 homers. He has submerged to new lows since then, however.

Despite a single and double tonight, he has only eight hits in his last 45 at-bats and six RBI in his last 43 games. Tettleton has struck out 12 times in his last nine games.

For the season he has 131 strikeouts, having already surpassed Boog Powell's team record of 125 in 150 fewer at-bats. Both he and Manager Frank Robinson say they've seen improvement in Tettleton's swing the past three weeks, but the results haven't followed.

"I have hit some balls hard, and I don't have anything to show for it," Tettleton said before tonight's game. "All I can do is hit them, I can't guide them. . . . I'm not jumping ship or anything. I'll keep going out there, keep working hard and hopefully it'll turn around." Milacki Ready, But Able?

Pitcher Bob Milacki threw for 15 minutes today and said he hopes to be ready for a start by the conclusion of the team's upcoming seven-game homestand. Milacki, who has a strained right shoulder, was eligible to come off the disabled list today, but Robinson said he's committed to his four-man rotation for now and hasn't given a thought yet to when he'll activate Milacki. . . .

The Orioles announced an agreement with the Perth Heat of the Australian Winter League. Baltimore will provide four Class A players to participate in the 42-game Australian schedule beginning in November. The Heat will be managed by Mike Young, the current manager of the Orioles' Class A affiliate in Wausau, Wis.