Chargers star DL Corey Liuget claims his former trainer injected him with PEDs without his consent and cost him over $15 MILLION ... and now he's suing to get that cash back.
The NFL stud -- who's been with the Chargers since '11 -- was suspended for the first 4 games of this season after testing positive for a banned substance.
Now, Liuget's filed a lawsuit ... pointing the finger at his longtime trainer -- Ian Danney.
Liuget claims he went to get treatment for broken foot bones in November 2017 .