It is not extremely fair. The team got a good deal because the player has to take into consideration his injury history (last year's back injury), plus his power numbers have declined. If he was still D. Wright of old, he would have asked for 8 for $160 mil extension on top of the $16 mil for 2013. But now the team signed him for 8 for $138 mil overall. Great deal for the Mets, safe deal for Wright.
Plus, if some of the money is deferred until after he retires, then they are making money on his money.