The Bills announced Dareus' suspension Tuesday afternoon but did not offer specifics. The positive marijuana test was first reported by NFL Network.
"We are very disappointed Marcell chose to put himself first, before his teammates, coaches, the rest of the organization, and fans through his recent actions," the Bills said in a statement. "From ownership down we have made it clear his behavior is unacceptable. We will continue to take the necessary steps to work with him in order that he adheres to the policies set forth by our league."
Dareus will forfeit $1.505 million in total compensation, which includes his signing bonus and option bonus. He took to Instagram to discuss his most recent suspension.
With deepest regrets I want to apologize to the @BuffaloBills organization, my fans, my family and the entire NFL football community for the incident that led to me missing 4 games for the upcoming 2016-2017 season. I will not #makeexcuses for the events in question and will allow the process to proceed as is required by the @NFL; however, please know and understand I am committed to the game and am more committed to my #Billsorganization and fans. This temporary setback will only fuel my desire and commitment to bring #Buffalochampionships and the #SuperBowl. I ask at this time that you continue to #believe in me and I will continue to invest all that I have to bring honor and respect to the organization and my fans and ultimately bring #Buffalomafia what it deserves - a #SuperBowl! Thank you for continuing to support me - I will rise above this setback, as with every challenge brings an opportunity for growth and supreme #success!
The sixth-year defensive tackle was previously suspended for the first game of the 2015 season for a violation of the substance-abuse policy following a May 2014 arrest in Alabama for criminal possession of a controlled substance.
The suspension is another blow to the Bills' defense, which lost starting outside linebacker Shaq Lawson to offseason shoulder surgery that is expected to keep him out until Week 6 at the earliest, a source told Schefter. Buffalo also will be without starting inside linebacker Reggie Ragland this season after he tore his ACL in training camp.
In the absence of Dareus, the Bills could turn to veterans Kyle Williams or Corbin Bryant to start at nose tackle in Rex Ryan's 3-4 defensive scheme. The team also signed a pair of veteran defensive linemen Monday -- Brandon Deaderick and Alameda Ta'amu -- to add depth.
In addition to Dareus, the team will be without second-year running back Karlos Williams for the first four games of the season for a violation of the NFL's substance-abuse policy. The Bills will be subject to a steep fine from the NFL based on the NFL's remittance policy -- the result of having multiple players suspended in a single season.
Dareus, 26, was named to the Pro Bowl in 2013 and 2014. The third-overall pick of the 2011 draft, Dareus signed a six-year, $100 million extension with the Bills last September.