I still expect they will sign a good DC and MC, which is why I think they'll be ok. Obviously if you play a defense of Smalling (lol), Jones, Evans, Blackett or whoever then it is going to be pretty shit, especially with Ashley Young and Jesse Lingard as wing backs.
I mean really, Van Gaal must know that is totally imbalanced, those are solely attacking players. Shaw and Valencia could pull it off, and obviously he was dealing with an injury crisis so thought that was the best he could do. He's got two right backs there (Varela, Vermijl) but played Lingard. It's one thing to go with the bold option, but the correct option is the only good one.