He was drafted by the Cincinnati Reds in the twelfth round of the 1988 Major League Baseball draft, and went 9–21 with a 2.80 earned run average and 72 saves over four seasons in their farm system to earn a call to Cincinnati in August. He gave up three earned runs in fourteen innings over the remainder of the season. Foster began the season with the Reds, but was optioned back to the triple ANashville Soundsin the beginning of May. He pitched exceptionally once he returned, going 0–1 with a 2.13 ERA and two saves. The one loss came in his one career start against the New York Mets. He began the season as Rob Dibble's set-up man, but began experiencing arm trouble toward the end of May. In one of the most notoriously strange baseball injuries, Foster landed on the disabled list with an inflammation of his right shoulder after a segment on The Tonight Show with Jay Leno in which he threw baseballs at milk bottles. After a monthlong trip to the DL, Foster returned for one appearance in June. After which, it was learned that Foster had detached cartilage in his right shoulder and would be out for the rest of the season. He had surgery, and began a rehab assignment with the Reds in Spring of. After suffering numerous setbacks, he had a second surgery in August. After three brief appearances with the Chattanooga Lookouts, his career was over.
Coaching
After his playing career, Foster worked as a scout with the Tampa Bay Rays in. He spent two years at the University of Michigan coaching a baseball camp for college students before returning to the Rays as a scout in &. In, he began managing the Wisconsin Woodchucks of the NorthwoodsCollegiate Summer Baseball League. Following the season, he resigned to become youth pastor at Highland Community Church in Wausau, Wisconsin. Foster returned to baseball in as pitching coach for the Florida Marlins' Class A South Atlantic League affiliate, the Greensboro Grasshoppers. After two seasons as a minor league coach, Foster became bullpen coach for the Florida Marlins from to, moving briefly into the pitching coach job toward the end of the 2007 season. On October 9, 2009, Foster declined the team's contract offer for the season. Shortly afterwards, he joined the Kansas City Royals organization. The Royals bullpen, ranked second to last in the majors in 2009 with a 5.02 ERA, showed modest improvement each season since Foster grabbed the reigns. On November 4, 2014, he was hired as the pitching coach for the Colorado Rockies.
Personal life
Foster is a devout Christian who, while serving as youth pastor at Highland Community Church, took the youth group on a missionary trip to the Dominican Republic. He and his wife, Cori, live in Frisco, Texas and have two children.