Van Persie's free-kick deflected off the wall and into the path of Chicharito, who sharply despatched an unstoppable shot past Al-Habsi with textbook technique. Turning on the style, van Persie powered his way through to sweep just over the top as it became a question of how many goals the Reds could net against deflated opponents.
Sir Alex decided to hand Chris Smalling and Shinji Kagawa a run-out at the expense of the flawless Rio Ferdinand and Carrick before Danny Welbeck replaced Young. The changes in personnel seemed to affect United's rhythm and Smalling caused a nervous moment with a back-pass before being booked for a foul on Kone.
To be fair, the defensive substitute was extremely fortunate not to receive a red card for the offence, which looked like a professional foul, and Jordi Gomez was inches away from dishing out his own punishment when his free-kick flew just wide of David De Gea's right-hand post.
The Reds still had the final say, though, as Van Persie got on the scoresheet again with a couple of minutes remaining. Rafael's flick led to an error by Beausejour which allowed Welbeck to unselfishly tee up the Dutchman. The leading scorer sent the ball back across Al-Habsi on the stretch for his 19th goal of his first season at Old Trafford.
Rarely are three points secured away from home in the Premier League as comfortably as this as United remain utterly determined to win back the title.