Keisler was drafted by the New York Yankees in the 2nd round of the 1998 MLB Draft out of LSU. He had previously been drafted by the Cleveland Indians in the 40th round of the 1995 MLB Draft and the 57th round of the 1996 MLB Draft and the New York Mets in the 40th round of the 1997 MLB Draft but did not sign with either of those teams. He signed with the Yankees on June 2, 1998. He was selected as the Yankees Minor League player of the Year in 2000 when he was a combined 14-5 with a 2.85 ERA in 28 starts for Double-A Norwich and AAA Columbus. Keisler made his Major League debut with the Yankees on September 10, 2000 against the Boston Red Sox, starting and pitching five innings to earn the win while allowing only one earned run. He appeared in 3 more games for the Yankees in 2000 out of the bullpen and then started 10 games for them in 2001. In his two seasons of part-time work he was 2-2 with a 7.19 ERA. He then missed the entire 2002 season while recovering from shoulder surgery he underwent in late 2001. In May 2002, Keisler, already on rehab with the shoulder injury, suffered a strange injury. While gardening, Keisler was bitten by a pygmy rattlesnake in his backyard. The Yankees released him in February, 2003.
Keisler signed as a free agent with the San Diego Padres on February 16, 2003 and made two starts with the Padres, while also appearing in 8 games for the AAA Portland Beavers. The Padres released him on June 5, 2003.
Texas Rangers/Houston Astros
He signed as a free agent with the Texas Rangers on June 16, 2003 and appeared in 5 games for the AAA Oklahoma RedHawks before he was released on July 14. Three days later he was signed by the Houston Astros and assigned to AAA New Orleans. He made nine starts and was 2-3 with a 4.28 ERA before becoming a free agent at the end of the season.
New York Mets
Keisler signed as a free agent with the New York Mets on February 17, 2004 and played the 2004 season with the AAA Norfolk Tides. He was 6-7 with a 3.81 ERA in 21 starts for the Tides.
He signed with the Cincinnati Reds as a free agent on November 12, 2004 and began the season with the AAA Louisville Bats where he was 5-2 in 12 appearances for a 2.88 ERA. He returned to the Majors on May 24 and made 24 appearances for the Reds in 2005, including 4 starts for a 2-1 record and 6.27 ERA.
He signed with the St. Louis Cardinals on November 16, 2006 but only made 4 appearances with the Cardinals, 3 of which were starts he finished 0-0 with a 5.19 ERA. He also made 24 starts for the AAA Memphis Redbirds and was 8-11 with a 4.79 ERA for the Redbirds.
Minnesota Twins/Chicago Cubs/Baltimore Orioles
Keisler signed a minor league contract with the Minnesota Twins on January 11,, but was released during spring training and signed a minor league contract with the Chicago Cubs. On June 3, he opted out of his contract and on June 10, he signed with the Baltimore Orioles. In 2008, he was a combined 6-9 with a 4.03 ERA in 20 starts for the Iowa Cubs and Norfolk Tides.
On March 3, 2011 he attended an open tryout, sponsored by the Los Angeles Dodgers and was signed to a Minor League contract He was assigned to the AAA Albuquerque Isotopes, where he appeared in 23 games and was 7-7 with a 4.67 ERA.
