Veteran left-hander Matt Thornton has decided to retire, reports ESPN’s Jerry Crasnick (on Twitter). The 40-year-old spent his final big league season in the Padres organization but was limited to 17 innings due to an Achilles strain and was released in mid-August.

Originally selected by the Mariners with the 22nd overall pick of the 1998 draft, Thornton didn’t make his big league debut until his age-27 season in 2004 and didn’t establish himself as a quality bullpen piece until his age-29 campaign. Traded from the Mariners to the White Sox in exchange for light-hitting outfielder Joe Borchard, though, Thornton blossomed on Chicago’s south side and eventually became one of the game’s premier left-handed setup men. From 2008-10, Thornton recorded a 2.70 ERA with 11.0 K/9 against 2.7 BB/9, showing a mastery over left-handed hitters and right-handed hitters alike thanks in large part to a fastball that averaged just shy of 96 mph.

Those three seasons may have represented Thornton’s peak, but the lefty was predominantly excellent for the better part of a decade from age 29 through age 38. In that time, Thornton recorded a 3.11 ERA and averaged just under a strikeout per inning. Overall, the lefty’s career will come to a close with a losing 36-46 record but a very solid 3.41 ERA, a 1.28 WHIP, 23 saves, 206 holds (164 of which came with the White Sox — a franchise record), 8.7 K/9, 3.4 BB/9 and a 48.2 percent ground-ball rate in 662 2/3 innings as a Major Leaguer. Thornton earned more than $28MM in his Major League career, per Baseball-Reference (plus a $925K signing bonus). We at MLBTR wish Thornton continued success in his post-playing days and offer a hearty congratulations on an impressive career.

Photo courtesy of USA Today Sports Images.