Montreal Expos

Fassero was drafted by the St. Louis Cardinals in the 22nd round of the 1984 amateur draft, but he bounced around in the minors for several years until he joined the Montreal Expos in 1991. At 28, Fassero was somewhat old for a rookie, but pitched well for the team and eventually made it to the starting rotation by the 1993 season. That same year he posted an impressive ERA of 2.29. He became a full-time starter during the 1994 season and had perhaps his finest year as a starter in 1996, earning 15 wins with 222 strikeouts and finishing ninth in NL Cy Young Award voting.

Seattle Mariners

On October 29, 1996, in a cost-cutting move, the Expos traded Fassero and Alex Pacheco to the Seattle Mariners in exchange for Chris Widger, Matt Wagner and Trey Moore. Fassero had one of his best seasons for the Mariners in 1997. That season he posted a 16-9 won-loss record with a 3.61 ERA in 35 starts.

Rangers, Red Sox, Cubs, Cardinals

Fassero enjoyed some stability during his time with the Mariners, but after a mid-season trade to the Texas Rangers in 1999, he would wind up playing on eight different teams in only seven seasons. He proved to no longer be effective as a regular starter, so he was moved into the bullpen. While with the St. Louis Cardinals, Fassero made six starts in the 2003 season, but only won one game.

Colorado Rockies and Arizona Diamondbacks

While with the Colorado Rockies in 2004, Fassero got into a dispute with Colorado management when he was called on to make a spot start on short notice.^[1] Fassero said that he would not be ready in time, and was subsequently released by the Rockies due to what then-manager Clint Hurdle called "philosophical differences".^[1]

He almost immediately signed with the Arizona Diamondbacks, but he only made one appearance with the team, pitching one perfect inning in relief.

San Francisco Giants

Fassero signed with the Giants on December 15, 2004, and remained on the team until May 8, 2006, when the Giants designated Fassero for assignment. The move cleared room on the team's roster for left-handed starting pitcher Noah Lowry.

On February 9, 2007, he announced his retirement.^[2] In the winter of 2008, though, Fassero pitched with Mayos de Navojoa in Liga Mexicana del Pacífico before he finally retired for good.^[3]

Minor League coach

Fassero was hired in December 2009 as the pitching coach for the Boise Hawks, a minor league affiliate of the Chicago Cubs in the Class 'A' short-season Northwest League.

For the 2011 season, Fassero was promoted to pitching coach^[4] of the Peoria Chiefs in the Midwest League.

Jeff Fassero received a promotion to the Double-A Tennessee Smokies (Chicago Cubs) for the 2012 season.

From 2014 to 2015, Fassero was the pitching coach for the Double-A Pensacola Blue Wahoos (Cincinnati Reds). He started the 2016 season as a roving pitching instructor for the Cincinnati Reds before being named pitching coach of the Triple-A Louisville Bats, taking over for the recently promoted Ted Power.^[5] Fassero is the current pitching coach for the Bats.