Per Tom Peliserro and Aaron Wilson, here is what Jeremy Lane's 4-year $23M contract looks like from a cap perspective for the Seahawks:
There is a rolling guarantee that vests in February 2017, if Seattle choose to cut Lane then they would take a $3.75M dead money hit versus taking a $5.25M cap hit if they kept him. So, unless Lane has a terrible year in 2016, I think there is a good shot he will be with Seattle for at least two years.
The cap hits are manageable in Year 1 and Year 2, and if he plays really well -- Seattle controls Lane in 2018 and 2019 at high numbers but not "chokingly high" numbers. I really like this deal for Seattle.