Don't get me wrong, I love when core players are locked up long-term. But when it's a "we have to see" guy I am always in favor of overpaying in the short term to mitigate the risk in the long term. It is a lot for one year, for sure. And I have been a guy that was against giving Fowler a 3-4 year deal averaging $10M+.
But to me what deals like this do is (a) keep the player motivated, (b) give the team flexibility, (c) get them better ROI on the 3rd rounder they gave up for him while (d) positioning them to recoup a compensatory pick should he leave in 2020.
To me Fowler is a 6-7 sacks guy. A nice piece. Maybe he surprises and produces more this year. I hope he does. But if you're interested in keeping a guy but not entirely sold on him this is the path to take.