Matt Barnes took a surprise shot to the stomach on his way into a NY courthouse Friday morning -- when a process server cut him off at the pass and smacked him with a lawsuit over his nightclub brawl.
The Golden State Warriors player had a scheduled hearing to take care of his misdemeanor assault citation from the Dec. 5 incident at Avenue nightclub ... in which he was accused of fighting two people in the V.I.P. section.
Barnes has said he only acted in self defense -- but the alleged victims filed a civil suit against Matt and DeMarcus Cousins demanding serious cash for their injuries.