He led the league in K’s and ERA, and had probably the worst run support in modern MLB history:

“In his 16 losses, he pitched 88 innings and got only 14 runs of support while in the game. Six times the Astros scored no runs for him, and eight times they scored only one run while he was pitching. Five times in 1987, Ryan left the game with a lead, only to see the bullpen blow the victory for him.”

No surprise that he left for the Rangers after the following season.