Just a few months ago, before she got (possibly fake) engaged to Casey Johnson, Tila Tequila was dating San Diego Chargers linebacker Shawne Merriman.

That relationship ended after an altercation at Merriman's house, in which Tila claims she was assaulted, but Merriman says he was merely protecting her.

She was plastered, he maintains, and he tried to keep a nude Tila Tequila from driving home drunk after turning down his generous offer to join a foursome.

The police did not charge Shawne, due to lack of evidence, which enraged Tila. She's suing Shawne for battery, false imprisonment and emotional distress.

Now the NFL star is suing back, claiming she's lying about what happened just to ruin his career ... and is also infringing upon his trademarked logo. Really.

Shawne Merriman says Tila Tequila is defaming him out of spite.

In his lawsuit, Merriman claims Tila lied when she said he "choked and attacked" her, "sleeps with minors and forces them to take drugs," and makes drugs at home.

Shawne claims in court docs that Tila Tequila admitted her lying scheme, even stating, "yes that is why I did a 'spin' now ... cuz now everyone is LOVINGGGG me."

We don't know what happened that night, nor do we necessarily believe Shawne. But Tila Tequila lying to get attention? Not exactly a huge stretch.

Merriman isn't only suing for defamation, either. He says Tila is also guilty of trademark infringement by using his quasi-famous "Lights Out" logo on her website.

The player also claims Tila's accusations screwed up a deal he was about to sign to produce a line of T-shirts for Walmart and says she interfered with his contract.