The frizzy-haired leading man who has stolen spotlights in American League parks from Boston to Anaheim found himself assuming center stage here this week on the mound in a Class A ballpark.

If the Mark Fidrych show plays to good reviews here, it could mean a return to the big time with the Detroit Tigers. If the show folds, it would mean the end to at 23 to what once looked like a brilliant career.

The bony right-hander is on assignment in baseball's bushes, performing his comeback act for the Lakeland team in the Florida State League. He's a $100,000 pitcher cast among $5,000 teammates.

Like Caruso trying to reprove his singing voice with a Lakeland barbershop quartet or Olivier beginning a comeback at the Polk County Little Theater, Fidrych is on the mend out of his league.

The Bird's first chance in this latest and most critical comeback was a three-inning stint Monday night against the Fort Myers Royals. Fidrych threw with zip and control, allowing two hits and one walk. Thirty-five pitches, 22 strikes and 13 balls.

Fidrych threw 63 pitches in four innings Friday against Winder Haven, yielding five runs, including an inside-the-park home run, in the 5-1 loss.

"I had control, I've got my rhythm back and I feel great," said the 23-year-old who was the American League rookie of the year in 1976 with a 19-9 record and the lowest earned-run average in the majors, 234.

But consider the risk each time Fidrych winds and throws under full power: One more tear, any return to disability, and the wonder of '76 could become the out-of-work has been of '78.

"If I let that worry me, I can't pitch anyway," he said. "All I know is pumping hard, firing with all I've got. If it hurts me, that's the way it goes. If I'm washed up, it won't be because I haven't tried.But I honestly think I'm back, all the way back."

After winning rookie honors in 1976, Fidrych suffered a knee injury March 21, 1977, underwent surgery and later returned to the mound. He compiled a 6-4 record that season before tendinitis in his right shoulder forced him out. He was placed on the disabled list in July and saw no more action that year.

This season, he was 2-0 with a 2.45 ERA in three appearances before the shoulder pain became so severe he could no longer pitch. He went on the disabled list May 1 and on July 20 was assigned to the Lakeland team as part of a recovery program.

Before he was sent to Lakeland, doctors tried everything in their medical volumes. For awhile, Fidrych seemed to improve. Then, as the Bird gave his right wing the major league test in April, he quickly limped away as lame as ever.

Early this month, Fidrych landed in a New York hospital. He was anesthetized and a doctor manipulated his right arm as if it were that of a Barbie doll, twisting it in ways that would have killed a conscious person with pain.

Scar tissue in that troubled shoulder was ripped loose and freedom of movement returned. More importantly, Fidrych could grip a baseball and fling it full force without pain.

His Detroit manager, Ralph Houk, sent him to Lakeland for three outings to see if the improvement was real and to determine if Fidrych was headed back to the Tigers or headed for unemployment.

The Monday crowd at Park T. Pigott Memorial Stadium was 3,000, a nice turnout for a FSL a game but far from the roar of 55,000 to which the Bird became accustomed during his marvelous year of 1976 in Detroit.

Fidrych pranced playfully around the Fort Myers mound, just as he did in Tiger Stadium. He fell to his knees and smoothed the dirt in front of the rubber. He talked to himself, or as some always suggest, talked to the baseball.

"As long as I'm here, I'll bust my butt to help Lakeland win the pennant," he said. "If I thought I was throwing bad and hurting Lakeland's chances, I wouldn't want to be here. I rehurt my arm once by pitching before I was well. I am not making that mistake again."

Houk ordered three innings for Monday night, and Fidrych went four Friday night. Then, in what the Bird hopes will end his return to Class A ball, he will pitch Tuesday and Saturday before "heading back where I belong."

The date of Aug. 9 and a Detroit game with the Texas Rangers is bounding around inside Fidrych's head. It could be his first big league chance since April 17. He thinks he's ready. "I know it," he said. CAPTION:

Picture, Mark Fidrych keeps his arm wrapped in a towel between innings of a pitching stint for Tiger farm team in Lakeland, Fla, UPI