Keisler has also totaled six seasons in the Major Leagues with five different teams. He began his career with the New York Yankees, combining for a 2-2 record in 14 games (11 starts) in 2000 and 2001. The Texas native has also spent time with the San Diego Padres, Cincinnati Reds, Oakland Athletics, and St. Louis Cardinals. For his Major League career, Keisler has totaled a 4-4 record in 55 games (20 starts) and has struck out 100 batters in 150 and two-thirds innings.

The 34-year-old began the 2010 season with Laguna in the Mexican League, where he posted a 3-3 record along with a 3.98 ERA in seven starts. The left-hander spent 2009 with the Southern Maryland Blue Crabs and compiled a 2-2 record in six starts. His best season came in 2000 with Triple-A Columbus, when he went 8-3 with a 3.02 ERA in 17 starts. Keisler was originally drafted by the Yankees in the second round of the 1998 amateur draft.