Matthew Olson Guerrier (born August 2, 1978, in Cleveland, Ohio) is an American Major League Baseball relief pitcher for the Los Angeles Dodgers. He attended college at Kent State University, and made his major league debut on June 17, 2004.
Guerrier was drafted by the Chicago White Sox in the 10th round of the 1999 MLB Draft out of Kent State University. (He had previously been drafted by the Kansas City Royals in the 33rd round in 1996 but did not sign.) He pitched in the White Sox minor league system through 2001, reaching AAA with the Charlotte Knights.
On March 27, 2002 he was traded by the White Sox to the Pittsburgh Pirates for Damaso Marte. He spent the next two seasons pitching in AAA for the Nashville Sounds.