BRADENTON, FLA. -- The worst thing happened to Andy Van Slyke last April 1, just when he was ready to have his best season: he was traded by pennant contender St. Louis to the perennially poor Pittsburgh Pirates.

The thought of leaving the Cardinals, a team that drew 3 million spectators in 1987, to join one that sometimes attracts minor league-sized crowds was more chilling than an October night game in Candlestick Park.

Van Slyke couldn't have imagined a crueler April Fool's Day joke.

"I went from the penthouse to the cellar in one day, from the penthouse to the boiler room," Van Slyke said. "I wasn't happy.

"My concept of Pittsburgh was that only a few thousand people showed up for the games. I had a very narrow-minded view of what it was like . . . and if I hadn't had such a negative view, I would have realized that Pittsburgh was potentially a great baseball town."

He never publicly criticized the trade, but Van Slyke didn't begin weighing the positives against the negatives until he got settled in a new home and moved out of the downtown hotel where he lived for six weeks.

"But I finally realized I had an opportunity to get out of the platoon system I'd be in with St. Louis and go on to bigger things," he said. "Once I started relaxing and playing to my ability, things got easier at the ballpark."

Van Slyke, considered by the Pirates the key player in the four-man deal that sent catcher Tony Pena to St. Louis, wound up enjoying the best all-around season by a Pirate since Dave Parker was in his most valuable player prime.

Van Slyke didn't post superstar numbers, but batted .293 with 21 home runs and 82 runs batted in. And he played so solidly -- and, often, spectacularly -- in center field that Manager Jim Leyland was obviously disappointed when he didn't win a Gold Glove.

"All you've got to do with Andy is put his name down on the lineup card every day," said Leyland, who played Van Slyke in all but five of the Pirates' 162 games.

"He will find a way to win a game for you, whether it's with a big hit or making a great catch or throwing out a runner."

Van Slyke, 27, might have left one of the best of teams -- St. Louis won the NL pennant -- but he wound up having the best of times.

"Once I got back home to St. Louis after the season ended, I realized I'd had more fun playing in Pittsburgh than I ever had in my career," he said. "The main reason was that I got to play every day.

"I went to the World Series in '85 with St. Louis but I wasn't a main ingredient in that puzzle over there. That kind of upset me because I never felt I was used to the fullest of my ability. It's unfortunate because I feel they could have had a pretty good ballplayer on their hands if they'd just set me free a little bit."

Van Slyke's statistics have gotten better in each of his five big league seasons, and he sees no reason his numbers shouldn't go up in 1988.

"If the guys in front of me get on more and I hit .300 and cut down on my strikeouts {he had 122 in 564 at-bats}, there's no reason why I can't have 90-plus RBI," he said.

He earned $550,000 last season, but will make nearly $300,000 more in 1988 after signing a one-year deal just before he would have gone to arbitration.

"The trade has enhanced my career immensely, not just because I get to play every day but financially as well," he said. " . . . And I'm excited about being part of something in Pittsburgh that hopefully will be very successful for the rest of the 1980s."