One thing the Bills can do to free up cap space is extend Dareus now...it would look something like this..
7 Years, $121 million, $25 million signing bonus; $55 million guaranteed ($30 million paid on first day of league year 2016)
Year 1: SB allocation $3.57M and Salary $2 million -- reduces cap hit to $5.57 Million from $8.6 million
Year 2: SB allocation $3.57M, Guarantee allocation $5 million, Salary $9 million - Cap Hit $17.57 million
Year 3: SB allocation $3.57M, Guarantee allocation $5 million, Salary $11 million-Cap Hit $19.57 million
Year 4: SB allocation $3.57M, Guarantee allocation $5 million, Salary $11 million-Cap Hit $19.57 million
Year 5: SB allocation $3.57M, Guarantee allocation $5 million, Salary $11 million-Cap Hit $19.57 million
Year 6: SB allocation $3.57M, Guarantee allocation $5 million, Salary $12 million--Cap Hit $20.57 million
Year 7: SB allocation $3.57M, Guarantee allocation $5 million, Salary $12 million-Cap Hit $20.57 million
He entered the league at 20 so he is only 25 -- 7 years is reasonable...