A righthander from Virginia, Thomas made his debut with the Astros in 1977, posting a 2.84 ERA in 6-1/3rd innings over four games. But he was waived after the season and claimed by the Cardinals where he pitched for three seasons then tossed four seasons with the Mariners. For his career, he compiled a 20-11 record with seven saves and a 3.82 ERA over eight seasons.