It really isn't hard to notice Manchester United's greatest weakness at the moment—their defence, which conceded 24 goals in the league so far, negatively stands out as the main area the Red Devils need to improve.
With Nemanja Vidic, Chris Smalling and Phil Jones having injury problems, the back four of Rafael, Jonny Evans, Rio Ferdinand and Patrice Evra has at times put in worryingly indifferent displays that have already cost United points in the league.
Here's a player-by-player analysis of United's defence:
David de Gea is an outstanding goalkeeper. However, the 22-year-old still hasn't ensured his place in the starting XI despite his recent run of fantastic performances—the Spaniard has to improve at catching crosses and has to stop conceding easily avoidable goals.
Rafael has evolved rapidly since the start of the season, has already made the right-back spot his own and is probably the best United defender at the moment. If he can continue this rapid progress, the United full-back could perhaps be the greatest right-back in the world in a few years' time.
Meanwhile, Evra continues to perform well on a regular basis despite his age, but it is clear the Red Devils will need a long-term solution to the left-back spot.
Alexander Büttner is an interesting alternative, but the former Vitesse man has seldom experience at the top level.
Furthermore, it is as obvious as ever that Evra is not the leader United need in the defence.
Evans is another United defender who performs decently, but, just like everyone else, the Northern Irishman has plenty of room to evolve. For instance, Evans needs to work on his discipline and stop making those needless fouls.
It is obvious Ferdinand's days are long behind him. The once-great defender has started becoming a liability in defence, with his teammates having to bail him out on several occasions.
No longer are his reflexes as sharp and his movement as brisk as they once used to be.
It seems like United's defence is playing fantastically, but it is far from the truth.
Each player is great individually, but once they are combined they create one of the most unstable defences in the Premier League.
Nobody can tell for sure, but Sir Alex's constant experimenting with the squad is doing them little good, and the fans will be happy to see Vidic return fully fit.
Once he completes his recovery, United could possibly have the greatest defence in the league, but until that happens Sir Alex needs to sort his defenders out.