If we were to suffer injuries to key players then we would struggle but then the same is true of any team in the PL. I just don't see that the likes of West Ham, B'burn, Pompey Everton etc are that much stronger in depth than us that they wouldn't struggle with injuries to key players.
Assuming that we are not unduly unlucky with injuries, that we buy a decent RB and a couple of other squad players then 5th-7th is not unrealistic.