Luke Gregerson, a right-handed relief pitcher, began his Major League Baseball career with the San Diego Padres. Drafted by the St. Louis Cardinals in 2006, he was traded to the Padres in 2009 before making his MLB debut. Gregerson quickly established himself as a reliable arm in the Padres' bullpen, known for his effective slider and ability to induce ground balls. During his time with San Diego, he became a staple in late-inning situations, often serving as a setup man.

In 2014, Gregerson joined the Oakland Athletics. His tenure with the A's further solidified his reputation as a dependable reliever. He continued to excel in high-pressure situations, maintaining a low earned run average and contributing to the team's bullpen strength. His performance with Oakland caught the attention of the Houston Astros, who signed him in 2015.

Gregerson's stint with the Astros was marked by consistent performances and leadership in the bullpen. He played a crucial role in the team's success, particularly during the 2017 season when the Astros won the World Series. Although he was not the team's closer, his contributions in the middle and late innings were vital to the Astros' championship run.

After his time with Houston, Gregerson returned to the St. Louis Cardinals in 2018, the team that originally drafted him.