Jason Frasor's journey in Major League Baseball began when he was drafted by the Detroit Tigers in the 33rd round of the 1999 MLB Draft. However, it was with the Toronto Blue Jays that he would spend the majority of his career, becoming a reliable presence in their bullpen. Frasor, a right-handed pitcher, made his MLB debut with the Blue Jays in 2004. Over the years, he developed a reputation for his consistency and ability to handle high-pressure situations.

During his time with the Blue Jays, Frasor became known for his effective use of a fastball-slider combination, which kept hitters off balance. His role primarily as a relief pitcher saw him frequently called upon in late-inning situations, where he often excelled. Frasor's tenure with Toronto was marked by several seasons where he posted impressive strikeout rates and maintained a solid earned run average (ERA).

In 2011, Frasor was traded to the Chicago White Sox, but his time there was short-lived. He returned to the Blue Jays in 2012, continuing to provide stability in their bullpen. His second stint with Toronto further solidified his reputation as a dependable reliever. Frasor's ability to adapt and perform in various roles within the bullpen made him a valuable asset to the teams he played for.

After his time with the Blue Jays, Frasor went on to play for the Texas Rangers and the Kansas City Royals. With the Royals, he was part of the team during their 2014 postseason run, which culminated in an appearance in the World Series. Although the Royals did not win the championship that year, Frasor's contributions during the season and playoffs were appreciated by the team and its fans.

Frasor's career concluded with a brief stint with the Atlanta Braves in 2015.