He became the odd-man out with Buffalo carrying four other running backs, including fullback Jerome Felton.
The Bills rewarded Dareus by making him their top-paid player with an extension that runs through 2021, and kicks in after the final year of his existing contract expires this season.
The NFL suspension stemmed from Dareus being charged with possession of a controlled substance and drug paraphernalia after being stopped by Alabama State Police on May 5, 2014. He avoided trial, during which he would have faced felony drug charges, by agreeing to enter an NFL substance abuse program.
"Man, it just feels like a weight's been lifted off my shoulders," he said. "It always feels good to be wanted and to know that the Buffalo Bills have committed to me like I've been committed to them."
The Bills freed up a roster spot for Dareus by releasing running back Bryce Brown, who was inactive on Sunday and used sparingly all preseason. Brown was acquired in a trade with Philadelphia in May 2014 and appeared in just seven games last season.

"He's the $100-million man now," Williams said. "We expect a lot from him and he understands that."
ORCHARD PARK, N.Y. (AP) — Star defensive tackle Marcell Dareus rejoined the Bills on Tuesday with his future secure and his past in perspective.
"Last week,NFL Jerseys From China, really took a lot out of me not being here,NFL Jerseys Cheap," Dareus said. "It took enough out of me to know that I need to really take this seriously. I'm happy I turned my life around and really just kind of put the best foot forward."
Four weeks after the arrest in Alabama,Wholesale China Jerseys, Dareus crashed his Jaguar into a tree near a busy suburban Buffalo intersection shortly after a Bills practice. He has since reached a plea agreement to have misdemeanor charges dropped.
Better yet,NFL Jerseys China, Dareus' return coincides with the Bills preparing to host AFC East rival and Super Bowl champion New England Patriots on Sunday.
Now he gets an opportunity to start proving himself on the field anchoring one of the league's most talented defensive fronts rounded out by Kyle Williams, Mario Williams and Jerry Hughes.
Signing a six-year, $108 million contract extension at the same time he was serving a one-game suspension for violating the NFL's substance abuse policy provided Dareus an opportunity to reflect. Dareus watched on TV as the Bills beat Indianapolis in their opener on Sunday.
Dareus is a two-time Pro Bowl and one-time All-Pro selection. He's been a four-year starter since being picked third overall in the 2011 draft. The 25-year-old is regarded as one of the NFL's top young lineman,Nike Air Max 95 White, and coming off a season in which he led the league's defensive tackles with a career-best 10 sacks.
The only question marks have been off the field,Wholesale Jerseys China.
"Happy to be back, of course, and knowing that Brady's going to be out there just gives it a little bit more fire," he said.
"I've got thick blood. I don't get cold easy," said Dareus, breaking into a laugh. "I'm a Buffalonian now."
Dareus is from Alabama, where he also played at college. He now considers Buffalo his home — and that includes the region's harsh winters.
Safety Aaron Williams was among Bills player eager to welcome back Dareus.
"We're in the future now," Dareus said. "I'm not even going to pull that back up."