It's disappointing Diaz left, and we absolutely miss him. But the football guys played that one right. They approached him early enough to renew his contract, it was clear he didn't want to sign (either at all or on mutually acceptable terms) so, with regret, they sold him, got a decent fee and reinvested that into the squad.
Which was exactly what we should have done with any number of other players in the past, most notably Trent and Konate in recent history. Give them enough time to sign and sell them if they don't, while we still can. I can kind of understand Trent as, with Klopp leaving, it was harder to sell the next five years, same reason Mo and Virgil went down to the wire. Konate less so. We should have been in advanced talks with him this time last year at the latest and should have sold him in the summer if he hadn't signed by then. We'd have only lost 12 months of him (not a great loss given the season he's having) and could have pushed harder and earlier for Guehi in to replace him.
Based on my understanding of their contracts, we should be having those discussions now with Alisson, Gomez and Curtis, and should be opening discussions with Dom, Mac and Gravy in the summer with a view to being well progressed this time next year. I'm assuming we'd be looking at exits for Ramsay, Harvey, Kostas, Mo, Endo, VVD and Bajcetic, whose deals are also up in summer 2027, meaning next summer is the last opportunity to get decent fees for them / or to shift their wages off the books if they're not looking up to scratch by then.
This whole thing of keeping players past their sell-by date, no matter how good they are, has to stop.