Casey Janssen, 4.8 fWAR
Drafted by Toronto in 2004, Casey Janssen spent eight seasons pitching for the Blue Jays, accumulating a 4.8 fWAR over that time.
He began his career in the rotation, starting 17 games in 2006, but didn't find much success and finished the season with a 6-10 record and 5.07 ERA. He found his niche when the team transitioned him to a relief role.
The righty made 70 appearances in 2007, pitching to a 2.35 ERA and recording six saves in 72-2/3 innings. He was effective early in his career despite not having a big swing-and-miss arsenal. He finished his first season in the bullpen with a 4.83 K/9 and 13.1 percent strikeout rate. These days, you'd have a hard time finding a job in a major league bullpen with those numbers.
Janssen had success with weak ground balls. He ran a 50.8 percent ground ball rate and 27.2 percent hard-hit rate in the first three years of his career.
The fourth-round draft pick came into his own in the back half of his Jays tenure. From 2010 to 2014, he developed more strikeout ability to the tune of 8.20 K/9. He took over the closer's role in his last three seasons with the team, recording 83 saves.
His 94.4 percent save percentage (34 saves in 36 chances) in 2013 ranks as the fourth-highest single-season save percentage in club history. He even has the second-most consecutive save opportunities converted, with 24 straight across 2013 and 2014.
Janssen finished his Blue Jays career with 90 saves, fifth all-time, and a 2.92 ERA in 375 2/3 innings before leaving in free agency following the 2014 season. He played one more year in the big leagues with the Washington Nationals. He signed with the San Diego Padres and Boston Red Sox in 2016 but never made it back to the majors.
Next: This Blue Jays reliever leads all pitchers in appearances in franchise history