NASHVILLE, Tenn. — Tennessee Titans left tackle Taylor Lewan is facing a suspension after a test came up positive for the banned substance ostarine, according to a post he made via social media Wednesday.

A source told ESPN’s Adam Schefter that Lewan’s A sample tested positive this summer, but results on his B sample are still pending and have yet to come back from the lab.

Lewan, who can dispute the test results in an appeal, said he didn’t knowingly use a banned substance and posted apparent polygraph results on Instagram. He also said his supplements were tested by a third party.

Lewan can dispute the test results in an appeal. If the B sample matches the A sample, he would face a mandatory four-game suspension as a first-time offender.

Lewan became the league’s highest-paid offensive lineman last season after signing a five-year, $80 million deal that included $50 million guaranteed.

The Titans open up the season with a tough stretch of games that includes the Browns, Colts, Jaguars and Falcons.