Suarez gave us 3 good years, and before we gave him a contract extension to 2021 (which was a dumb idea) his original contract was going to end in 2019 (so a 5 year contract deal that we'll probably give Antoine)
IF i were manager in this hypothetical where we never gave suarez a contract, I would of attempted to sell him in summer of 2018 with 1 year left to either MLS, China or wherever will give maybe 1/4th the price we paid for him. (20ish million)
which is what we should do with griezman... will we make a loss? sure but the point is to get a prime player ready to improve the team.. would we have won the treble without Suarez? probably not.
clearly it's not an easy decision but this idea of people being scared of giving a 27/28 y/o a 5 year contract isn't a one sided bad solution.
also this is worth case scenario not all plays start declining massively straight at 30/31