Petkovsek was a first-round pick of the Rangers in 1987, and in 1991, he made his major-league debut with the club, pitching 42⁄3 innings and taking the loss against the New York Yankees.
The Rangers granted him his free agency following the year, and he signed with Pittsburgh for 1992. He spent the year at AAA Buffalo, where he co-aced for the club with Tim Wakefield.
After Petkovsek appeared in 23 games for Pittsburgh in 1993, the Pirates let Petkovsek walk, and the right-hander signed with the Astros for 1994. They assigned him to AAA Tucson out of spring training, and he spent the entire year there.
On May 16, 1994, Petkovsek threw the first nine-inning no-hitter in Tucson franchise history,[2] beating the Colorado Springs Sky Sox, 5–0, in his only complete game of the year. For his effort, Petkovsek was named PCL Pitcher of the Week.
As had the Rangers and Pirates before them, the Astros granted Petkovsek his free agency after the 1994 season, and he found a home in the Cardinals organization, pitching at both AAA Louisville and for the major-league team in 1995. His 21 major league starts that year were a career high.
He helped the Cardinals win the 1996 National League Central division title, winning 11 times against only two defeats as a swingman. The 11 wins he had for St. Louis were a career high, regardless of professional level.
