CLEVELAND -- Browns backup center Ryan Seymour has been suspended by the NFL without pay for this season's first four games for taking a banned substance.
The league said Monday that Seymour violated its policy on performance enhancing substances. The league did not say which substance Seymour, who started three games for Cleveland last season, used.
Seymour expressed remorse in a statement.
"Although I did not knowingly take a substance that was on the NFL's banned list, I do know that as an NFL player I must take full responsibility for everything that is in my body," he said. "I will be much more careful in the future so something like this never happens again."
Seymour said he's disappointed he can't help the Browns as the season starts.
"I look forward to putting this behind me, and right now, I'm focused on continuing to work hard, being a good teammate and helping my team improve for the remainder of the preseason," he said.
Seymour can return to the Browns' active roster on Oct. 5, a day after they play in San Diego. The 6-foot-4, 305-pounder is eligible to participate in all preseason practices and exhibition games. Cleveland hosts Buffalo on Thursday night.
After being claimed off waivers last August, Seymour added depth to Cleveland's offensive line. He appeared in 11 games, making three starts after Pro Bowl center Alex Mack broke his left leg.
The 25-year-old was drafted in the seventh round by Seattle in 2013. He spent 14 weeks on the Seahawks practice squad before he was signed by San Francisco. The 49ers waived him at the end of camp last year.