Lyon made his major league debut halfway through the 2001 season, posting a respectable 5-4 record for the Toronto Blue Jays, with a 4.29 ERA from 11 starts. He was the second youngest winning pitcher in Blue Jays' history after winning on debut (2-1 over Baltimore).
2002, however, was a different story. Lyon started the season as a starter for the Jays, but lost three of his first four decisions of the season, including a career-high 7 earned runs against the Yankees on April 10, and against the Angels on May 3. Three weeks later, Lyon was kicked from the rotation, and placed in the bullpen. He made his debut in this role at the Skydome, against Boston, pitching 3 1/3 innings. In five games of relief, Lyon had no decisions against him with a 5.19 ERA. During the postseason, the Red Sox claimed Lyon off waivers.
Boston made Lyon a permanent reliever, and Lyon appeared in 49 games in 2003, converting 9 saves in 12 opportunities with 50 strikeouts in 59 innings pitched. Lyon missed the entire 2004 season due to injury, after having been traded along with Casey Fossum, Michael Goss and Jorge de la Rosa to Arizona in exchange for Curt Schilling.
Lyon improved in 2005, converting 14 saves in 15 opportunities while pitching in 32 games and spending part of the season as the Diamondbacks' closer, replacing the injured Jose Valverde. However, he spent most of the second half on the disabled list. In 2006, Lyon had a very solid season, posting a 2-4 record and a 3.89 ERA in 68 appearances. In 2007, Lyon had probably his best season yet, with a 6-4 record, 2 saves, and the best ERA of his career, at a sparkling 2.68 in 73 games. Lyon found his niche as the Diamondbacks' primary setup man, pitching in front of Valverde, as Arizona won the NL West division title. For most of 2008, Lyon served as the closer for the Diamondbacks following the offseason trade of Valverde to the Houston Astros. However, he lost the job to Chad Qualls following second-half struggles.
- ↑ Beck, Jason. "Lyon, Tigers agree to one-year deal: Righty becomes frontrunner for closer's job in Detroit bullpen", MLB.com, 24 January, 2009. Retrieved on 2009-01-24.