All boils down to what we've been missing since we've been back in the premiership and none of our managers have addressed. A quality number 10 who can open up defences through the middle. Teams come to SP, stop our wingers and we have to rely on free kicks and corners to win games.

This in a nutshell!

Developing a potent midfield has always been sidelined. When we have potentials to fill this role they are not encouraged (think Garvan, Bannan, Williams and now Lee) Little comes through the middle (hence the demise of Murray and Gayle) so the opposition only need to put 3 on to Zaha to make him go round in circles and fall over leaving our centre forward isolated with little amunition.
Our corners are not that much better. Puncheon is industrious but lacks ball control. With the advent of Sakho combining with Cabaye and Milosevic
things began to look better as they were features of our wins over Chelsea, Liverpool and Arsenal.
Now without Sakho we revert back to hoof balls and 'get rid of it quick' tactics.
If we go down the reason will be the lack of a functioning midfield.

You are quite right. Effective holding mid-fielders are like gold dust and we have not had any for many years. I can't help feeling that if we had employed a continental manager this ongoing problem would have been addressed.

I think if you look at the names you've mentioned and where they have ended up post Palace (barring Lee ofcourse) then you have answer as to why it's sidelined.

Finding a top quality creative midfielder is a challenge, and so far we've quite rightly not felt comfortable throwing our lightweight alternatives into the mix.