A native of Park Ridge, IL, the righthander made his big league debut in 2009 with San Diego. He spent five seasons there then one in Oakland before he was signed by Houston as a free agent for the 2015 season.

In three years with the Astros, he went 13-9 with a 3.66 ERA and 47 saves. Gregerson became a free agent after the 2017 season and signed with St. Louis. Through 2019, his overall record is 35-36 with a 3.15 ERA and 66 saves over 11 seasons.