Houston Astros pitcher Ryan Pressly tried to play the role of peacemaker with a heckler who was going after Roberto Osuna ... but Pressly ended up calling the guy a "dickhead" and walking away.
It all went down on Monday when the Astros were taking on the Cleveland Indians at Progressive Field for Game 3 of the ALDS ... when a CLE fan began teeing off on Osuna.
The person who shot the video says the heckler was going after Osuna about his domestic violence arrest -- yelling things like, "Do you remember baseball before you committed domestic violence?