The Steelers have exercised the 5th year option of David DeCastro’s contract according to Albert Breer of NFL Network.
https://twitter.com/AlbertBreer/status/586210494316470274
This move is pretty much a no brainer. The option gives the team the ability to retain rights to the player, and gives them time to work on a long term deal. For the player, the option amount is guaranteed upon injury.
The guarantee goes into effect March 8 of next year. If the team does not reach a long term deal with DeCastro before then, his 2016 cap number will be $8,070,000. That salary is determined by the average of the third through twenty-fifth highest salaries of offensive linemen.