He was brought up to Seattle in late May, and immediately became manager Chuck Cottier's favorite arm out of the bullpen. The Mariners set a franchise record with an eight-game winning streak in late June. Thomas appeared in three games during that stretch, and earned two wins while holding opposing batters to a .190 batting average. When fortunes reversed, and the M's were on a six-game losing streak in late July, Thomas pitched 6.1 brilliant innings of relief against the American League champion Boston Red Sox to break the streak. Despite having missed almost two months of the season, he pitched a team high 93.2 innings in relief, compiling a 7-0 record with a 3.36 ERA and seventy strikeouts. As a result, Thomas earned the distinction of having compiled the most wins without a loss ever on a team with a losing record when he went 7-0 for the 1985 Seattle Mariners (74-88). This record would be matched by Aaron Sele in the 2001 Mariners season.