Posted by Sabrina B. @gametimegirl

Thiago Silva knowingly attempted to alter the results of a urinalysis administered by the Nevada State Athletic Commission, the UFC light heavyweight admitted in a statement issued Wednesday.

In a complaint filed against the 28-year-old Brazilian mixed martial artist, the NSAC alleged that Silva’s urine specimen, taken before a Jan. 1 UFC bout versus Brandon Vera in Las Vegas, reflected a “complete-invalid result” indicating it was “inconsistent with human urine.” Silva is alleged to have substituted synthetic urine for his own, according to NSAC executive director Keith Kizer.

“I used a urine adulterant when giving a sample following my fight with Brandon Vera,” Silva is quoted as saying in a release issued by his manager, Dan Lambert. NSAC paperwork actually shows the test was administered before the bout, Kizer said.

“I did so in an attempt to alter the results of the test and knowingly broke the rules of the Nevada Athletic Commission. This was a terrible decision on my part for which I will be punished. I am prepared to accept this punishment, learn from it and move on. I apologize to the Commission, the UFC, Brandon Vera and the MMA fans.”

This is the first time Silva tested positive for a banned substance. He has tested clean on five other occasions, including one that required blood work in New Jersey. Forty-five days before his fight against Vera, Silva claimed he re-injured his back, an ailment that had kept him out of action for a year following a loss to Rashad Evans on Jan. 2, 2010.

WRITTEN BY Josh Gross covers mixed martial arts for ESPN.com & FULL STORY HERE