The New England Patriots will play the last four games of the regular season without rookie linebacker Brandon Spikes.

Ian Rapoport of the Boston Herald reports that Spikes has been suspended and has decided not to appeal so that he can serve his suspension immediately and return for the playoffs.

Spikes tested positive for a substance that is banned under the league’s policy on steroids and related substances.

Spikes has played in all 12 games this season, starting eight. He has 61 tackles.

UPDATE: Spikes released the following statement: “I’ve been contacted by the NFL and informed that I will be suspended 4 games for the detection of an illegal substance in a drug test. The substance was a medication that I should have gotten clarification on before taking. It was not a performance enhancer or an illegal drug. The integrity of the game is very important to me. I understand the league’s ruling and apologize to my teammates, the fans and the Patriots organization for this mistake.”