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After a shocking first half of the season in which goals were conceded at an alarming rate, Manchester United's defence has finally hit top form.
This has been mostly due to the return of Captain Fantastic, Nemanja Vidic, from injury, restoring a commanding authority to the back line.
The Red Devils have conceded only two goals in their last six games in all competitions, keeping clean sheets with an increasing regularity.
Along with Vidic, Rio Ferdinand has continued to defy those who have suggested retirement may be on the cards with controlled, intelligent performances, while the ever-improving Jonny Evans seems to have added a newfound physicality to his bow.
Rafael and Patrice Evra, full-backs previously criticised by fans and pundits alike, have been playing some of the best football of their respective careers.
Real may have some of the most potent attacking players in the game, but Sir Alex has the tools at his disposal to stop them.