Well, Shark's 4.31 xFIP wasn't exactly great last year either, so it's not just the ERA. Really hard to figure out what someone will give him, but he'll be 31 at the start of the year next year, so I don't see him taking a 1 year deal to rebuild value.
I don't think he'll get as much as Porcello, who was likely boosted quite a bit by age. I could see 5/75.