Claims Trainer Injected Him w/ PEDs

... Sues For $15 MIL!!

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 ... when Danney injected him with what he said was a "strong dose of an over-the-counter anti-inflammatory."

He says 2 days later he gave a urine sample ... and it came back dirty.

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