I lost a bet on Porcello last season. (Having me bet on someone is like the kiss of death for that player, and I should have known better than to bet, even though it was only a sig bet.) But I maintained that regardless of how poorly he pitched, and regardless of whether he bounced back this year or not, and regardless of whether he continues to pitch well for the remainder of his contract or not, the contract extension was a good bet.
Not knowing how the 4 years (plus one year from the old contract) would play out, I would do that deal all day every day, and twice on Sundays.