I'd let Skrtel go before Henderson, because as I've said many times I just don't rate him. He's 28 and should be at his peak as a centre back, but he's error prone, gives away too many free kicks and for me he's a bit of a softie when it comes to a physical battle (just because he's got a skinhead and tattoos doesn't impress me). Last summer was our best chance to make money on him though after he'd had a good season (his only good season I might add!). That said we've already lost Carra, Coates probably needs to go somewhere at least on loan to get football and Agger (last season apart) is an injury prone player, so can we afford more upheaval at the back? I'm not sure.
Henderson I probably wouldn't sell. He's improved and I've always said I think he'll turn out to be a good player. He's also the only midfielder we've got who genuinely has the legs to play box to box. Gerrard's days of that are gone, Lucas has never been the most mobile, while Allen is a sitter rather then a marauder.
That's the one area, even above centre back, that I'm concerned we haven't strengthened. And we don't even seem to be getting seriously linked with athletic central midfielder types. It'll see us come unstuck at the Britannia and Upton Park etc next season when teams get in our faces in the midfield, I have no doubt. Most fans can see it, surely that many people can't be wrong!