Sir Alex apparently was seeking to improve his defensive options in January, with Nemanja Vidic ruled out for the rest of the season through injury, but a transfer never materialised.
Now he might, and should, have to act soon, as mega-rich Anzhi Makhachkala are hoping to tie up a deal for the Serie A star, with the Russian transfer window not closing until Feb. 24.
It's clear the Red Devils need a new centre-back, with Rio Ferdinand losing his form, Jonny Evans continually error-prone, and both Chris Smalling and Phil Jones not yet experienced enough to be regular starting centre-backs.
And Mehdi Benatia is the right option.
The 24-year-old Morocco international, who again impressed at the African Cup of Nations, has been a revelation in Serie A this season, taking up the role as the Vidic or Vincent Kompany of Udinese.
Whilst he's not the most commanding in the air—although he does usually win at least one aerial duel per match—Benatia is a strong player in the tackle and has a higher tackle success rate than any United defender.
That's a quality which would come in really handy for the Red Devils, given that Evans and Ferdinand have given away deleterious fouls this season due to their poor tackling.
In terms of one of the main things Premier League defenders are judged for, interceptions, Benatia does it better than any member of the Champions' back four.
He makes 2.5 interceptions per game, which ranks higher than Vidic (2.3), Ferdinand (2.2), and much better than Jones (1.9), Evans (1.8) and Smalling (1.3).
As far as clearances go, Benatia's 7.5 per match aren't as good as Ferdinand's or Vidic's statistics, but he does outrank the other United defenders and blocks more shots per game than Ferdinand and Vidic put together.
His John Terry, put-the-body-on-the-line style has been vital for Udinese this term and that's another thing United's defence has seriously lacked in 2011-12.
But aside from the statistics, Benatia is an experienced professional who's racked up many games in Ligue 2, Ligue 1 and Serie A, and has won 13 caps for his country.
And he's only 24, so he has the pace and athleticism to keep up with the quick players and the upper body strength to out-muscle them.
His blend of great form, good experience and very good athleticism is the main thing lacking from the Manchester United defenders this season.
Plus, he's a versatile player who's equally as good defensively at right-back.
For the start of next season, the Old Trafford outfit need an experienced, reliable centre-back who's been in great form and has pace and power.
Benatia ticks all of these boxes, so if United are going to keep up with their noisy neighbours Manchester City in the coming seasons, and stave off the threat from Tottenham Hotspur, Chelsea, Arsenal and Liverpool, they need to beat vultures Anzhi Makhachkala to the signing of Benatia.
They may not be able to offer the untold riches available in Russia, but to avoid his career being wasted in the Russian Football Championship as much as their need for a player like him, Manchester United have to sign Mehdi Benatia.