Good contract for both parties. Humphries got a nice guaranteed sum and we don't need to totally overhaul the OL. This fact alone will help KM most importantly. Don't discount the trust factor between QB and LT as well.
It's a little bit of a prove-it deal, if you want so, for Humphries. He is still young and once his contract is up, or at least the guaranteed part of it, he will enter the prime age for a LT. If he indeed lives up to his potential and continues to be durable like last year, we shouldn't let him walk. No decent LT ever hits FA. Not even semi-decent ones. Veldher was the last one when Keim jumped on him and he was considered average at best and was older than Humphries.