The Bills sent Dareus home for violation of a team rule, Chris Brown of the Bills' official website confirmed.
There was no indication of the specific rule the 27-year-old broke. Dareus has found trouble since becoming a first-round pick in Buffalo in 2011. The defensive lineman has been suspended twice and arrested once in six seasons.
After two years under Rex Ryan giving his players plenty of rope, new coach Sean McDermott is cleaning up shop.
Dareus signed a seven-year, $103.2 million contract in 2015. He followed that up with a 2-sack season and earned 3.5 sacks in just eight games in 2016 due to injury. Dareus' start under the new regime isn't off to a blossoming beginning.
"Sean and I are going to do things the right way," Bills general manager Brandon Beane told reporters. "He violated a team rule, so we sent him home. Disappointing."
"It was a violation of a team rule. We're disappointed," McDermott said. "My hope is he'll learn from it and move forward."