Johnny Manziel's got more drama heading his way ... the guy he fought in a Vegas nightclub last month has lawyered up and is gearing up for a lawsuit, TMZ Sports has learned.
We broke the story ... the ex-NFL star was booted from Jewel Nightclub at the Aria hotel on May 20th after getting violent with another clubgoer.
Witnesses have said Manziel was pushed while the crowd was going crazy during a surprise performance by Drake -- and, during the madness, Manziel turned and slugged a guy.