I agree but it has become a bit more common recently. Lindelof and Fred both had troubled starts though both are no more than decent players. Shaw too, and he is one of the first names on the team sheet now. Looking back at top class players, Evra and Vidic both struggled early doors.
I don't know what VDB is doing in training that's so bad but i think we do need to give him a real chance in the first team before we write off a 35m investment, so in his proper position, and not paired with kids or OAPs. Plenty of players train badly yet still turn up on matchday.