Dareus, the third-overall pick in the 2011 NFL Draft, will receive a salary of $8.06 million in 2015 (fully guaranteed for injury) as a result of the Bills decision.
It was a pretty easy choice for Buffalo; Dareus has been a productive player in his three seasons with the Bills and pairs with Kyle Williams to form one of the better defensive tackle tandems in the NFL. (Add in Mario Williams on the end and they're a pretty formidable group.)
Plus there's limited risk for Buffalo and they buy an extra year to work out a long-term deal if they're so inclined.
Follow the full list of 2011 draftees with their options picked up here.