My guess is that Heitinga is injured (hence Fellaini) & Moyes feels Saha helps with headers from corners and set pieces (in both penalty areas), Cahill may drop a bit deeper and allow Billy & Pienaar to play off Saha. Going forward, they are not the best out wide (strong through the middle) so we don't need an extra defender to help Neville (like we did when we played Spurs). If Petrov, comes on, so will Coleman. Baines might hold back a bit too. Horses for courses, it shows a bit of bravery and thought has gone into it. Hope it works.