Zimmerman was purchased from Winnipeg by the Texas Rangers in 1998 and played at both the A and AA minor league levels. In 1999, he made his way onto the Rangers Major League squad after a short stint at the AAA minor league level. He became a very successful middle relief pitcher in the bullpen and even became an All-Star that season. Zimmerman tied the record for most consecutive winning decisions to start a career with nine wins. In 2001, he became the Rangers' closer and amassed 28 saves in a season that culminated in the Rangers naming him the club's Pitcher of the Year. Over the three years from 1999 through 2001, he totaled 17 wins, 32 saves, and a 3.27 ERA in 228 IP in 196 games. Following this trend of top performance, the Rangers rewarded Zimmerman with a three-year contract worth over $10 million. Unfortunately, Zimmerman suffered a series of injuries that prevented him from throwing another pitch in MLB, beginning with a spring training injury in 2002 and continuing through three major surgeries on his elbow, including two Tommy John surgeries. He did manage a handful of minor league and Arizona League games, but never close to a full season and never at the MLB level. Following the end of this contract, which covered 2002 through 2004, the Rangers reinvested in Zimmerman with a minor league contract for the 2005 season. Again Zimmerman suffered injuries that prevented his return to the field of play for the course of the entire season. Zimmerman elected to take the 2006 season off in hopes that his arm would naturally heal over the course of the season. T. R. Sullivan, the Rangers' beat writer on MLB.com, called this decision "his last, best hope" for returning to playing baseball. Having not competed in a game since 2003, Zimmerman retired in 2006 and moved back to Vancouver, British Columbia. In 2008, The Sports Network listed Zimmerman as retired and gives his career potential as, "After four years out with injuries, he may be done." On January 18, 2006 Lone Star Ball, a Texas Rangers blog, named Zimmerman 46 on "The 50 Greatest Rangers of All Time" list.
On April 7, 2009, Zimmerman came out of retirement, signing a minor league deal with the Seattle Mariners. He spent the first several weeks of the season in extended spring training. Zimmerman, who had been plagued with injuries for most of his career, said this about his baseball abilities after sitting out for so long: Zimmerman appeared in one game for the Arizona League Mariners, pitching two innings and giving up one run. He has not pitched professionally since.
