New York: Denver Broncos defensive tackle Derek Wolfe will miss the first four games of the 2015 NFL season after testing positive for a performance-enhancing drug, the league said on Friday.

In a statement released by the Broncos, Wolfe said he took a medication in the off-season that he did not realise was on the banned list.

“I was genuinely unaware it was prohibited,” Wolfe said. “But players are responsible for what is in their bodies. I will certainly exercise far greater caution in the future and will seek advice relating to the permissibility of any and all medications.”

Wolfe will be able to take part in training camp and preseason games before serving his four-game suspension.

Two further suspensions for players violating NFL policies on “substances of abuse” — which are treated differently from performance-enhancing drugs — were announced on Friday.

The Kansas City Chiefs said cornerback Sean Smith will miss the first three games of the regular season after pleading guilty in April to a 2014 drink-driving charge.

NFL.com reported that Smith was banned for three games — rather than two — because he hit a street lamp in the incident.

Minnesota cornerback Jabari Price will miss the first two games of the season after pleading guilty in April to careless driving after a December drink-driving arrest.

Price, 22, apologised for the incident in a statement released by the Vikings.

“I can assure you that it will never happen again,” he said. “I look forward to returning to helping my team on the field in week three.”