Nicknamed "Boomer" for his portly physique (6-3, listed at 240 pounds but thought to be more) and off-field interests such as Harley-Davidson motorcycles, Wells was a journeyman starter for the first eight seasons of his career. He debuted for the Toronto Blue Jays in 1987 as a reliever and did not secure a job as a full-time starter until he was 30 years old, despite pitching well most of the time.
He emerged as a top-flight pitcher in 1995, when he was 32. After starting the year at 10-3 for the last-place Detroit Tigers, he was traded to the Cincinnati Reds shortly after making his first All-Star Game appearance. He finished that season with a 16-8 record and a 3.04 ERA.
In 1997, he signed as a free agent with the New York Yankees, his favorite team because of a lifelong interest in baseball legend Babe Ruth, taking the jersey number 33 in deference to Ruth's long retired number 3. After posting a 16-10 mark in 1997, Wells pitched brilliantly in the Yankees' record-setting 1998 season. He rung up an 18-4 record, finished fifth in the league in ERA (3.49) and was third in voting for the Cy Young Award.
On May 17, 1998, Wells became the 15th pitcher in major league history to pitch a perfect game when he blanked the Minnesota Twins, 4-0. In an interesting historic note, Wells attended the same San Diego high school as Don Larsen, whose perfect game for the Yankees in the 1956 World Series remains the only no-hitter ever thrown in postseason play.
After the season, he was traded back to the Blue Jays for Roger Clemens, but continued to win north of the border, with records of 17-10 and 20-8 over the next two years.
After an injury-plagued 2001 season with the Chicago White Sox, he returned to the Yankees. Despite having lost some velocity from his fastball, he retained his excellent curveball and his control, and posted an outstanding 19-7 record in 2002.
Wells was the subject of some controversy prior to the 2003 season, when his autobiography Perfect I'm Not: Boomer on Beer, Brawls, Backaches and Baseball, was published. The book upset the Yankees' management, and Wells was fined $100,000 by the team for disparaging comments which appeared in it. The problems didn't carry over to the field, however. Wells posted a 15-7 record and helped the Yankees win another pennant.
On September 28, 2003, the final day of the regular season, Wells earned the 200th win of his career in a game managed by Clemens, who had won his 300th game earlier in the season and was retiring from baseball. Regular Yankees manager Joe Torre let Clemens manage the last, meaningless game of the regular season, and Clemens pulled Wells from the game in the eighth inning.
At the end of the 2003 season, Wells owned a career record of 200-128, including a 137-75 mark since 1995. His career ERA of 4.06 looks unimpressive, but it is above average for the big-hitting era in which he's had his best seasons.
On January 1st, 2004, Wells was signed by the San Diego Padres.