5. The Inexperience of Danny Welbeck
When you think of the four strikers United have at Old Trafford, Danny Welbeck sticks out as the weak link. That's not to be unkind - he is only 22 and has a lot of maturing to do. Of United's four strikers he is certainly the more inexperienced. He has spent loan spells at Preston Northend and Sunderland where he scored a combined eight goals, and upon his return to Old Trafford from loan he managed an impressive 12 strikes last season. But at the moment he isn't a 15-20 goal-a-season player. Lewandowski on the other hand has scored 40 league goals in 83 games for Borussia Dortmund and 15 goals in 25 appearances this season. That's the sort of goal-scoring record you want out of one of your main strikers, and Welbeck just isn't managing that right now.