Tewksbury was drafted by the New York Yankees in the 19th Round of the 1981 Draft. After a number of seasons in the minors, Tewksbury was called up in April of 1986 and made his debut on April 11, 1986. He would pitch during the 1986 and part of the 1987 season for the Yankees before being sent down to the Yankees AAA affiliate Columbus Clippers. His demotion caused Tewksbury to ask for a trade.
His wishes were granted with his being traded on July 13, 1987 with Rich Scheid and Dean Wilkins to the Chicago Cubs for pitcher Steve Trout in one of the many lopsided trades the Yankees seemed to fall prey to during the late 1980's. Trout went 0-4 wth a 6.60 ERA in his only season with the Yankees and would himself be traded with Henry Cotto to the Seattle Mariners for Lee Guetterman, Clay Parker and Wade Taylor.
Tewksbury never really seemed to find himself in his season and a half with the Cubs going 0-4 with a 6.75 ERA in only 8 games pitched. He would be granted free agency and signed with the St. Louis Cardinals. It was with the Cardinals that he would show flashes of his limited walk potential.
In six seasons with the Cardinals (968.2 IP), Tewksbury walked a total of 125. That's an average of almost 21 walks in an average of 161 innings pitched. Here are the number of innings and walks during his six years in St. Louis: