Deshaun Watson just stepped foot on an NFL field for the first time in 700 days ... and the Houston Texans fans made their displeasure known -- letting the boo birds fly as he made his Cleveland Browns debut.
The 27-year-old quarterback is returning from an 11-game suspension for violating the league's personal conduct policy ... after dozens of massage therapists made sexual misconduct allegations against him.
Watson faced a hostile crowd as he made his Browns debut on Sunday .