According to the Buffalo News, Dareus got hurt in practice and was able to walk off the field without help.
Per the report, Dareus's left ankle was heavily wrapped.
Dareus isn't expected to play in Saturday night's preseason game against the Jacksonville Jaguars.
Dareus was off to a fast start to his NFL career with the third overall pick of the draft recording two sacks in two preseason games.
For more coverage of the NFL, go to our home page at www.profootball.scout.com