The full-back slammed a stunning half-volley into the top corner from 25 yards to put United ahead in the 23rd minute on a cagey afternoon in west London.
Ryan Giggs sealed the points for the league leaders 10 minutes from time as he beat QPR’s offside trap to sweep the ball home.
The only concern for United will be the apparent back injury that forced top scorer Robin van Persie off five minutes before half-time after a collision on the touchline.
QPR manager Harry Redknapp recalled much-criticised defender Jose Bosingwa for the first time since December 9 with Fabio ineligible against his parent club, while Bobby Zamora led the attack for the hosts.
United started with a strong line-up as Van Persie returned to partner Chicharito in attack while Wayne Rooney was well enough to take a place on the bench after suffering a virus.
Redknapp called for a cup-tie atmosphere before kick-off as he targets 20 points to guide QPR to safety, and the crowd responded as they backed their side and jeered the league leaders, particularly Ashley Young after the winger’s dive to win a penalty against them last term.
After a tepid start to the game, United took the lead in the 23rd minute with a goal from nowhere. Julio Cesar parried away Van Persie’s initial cross-cum-shot and the ball fell for Rafael to crack an outstanding half-volley into the top corner from 25 yards. The Brazilian will likely never score a better goal in his life.
At the other end, Rafael was on hand in the 35th minute to deny QPR an equaliser as he cleared Christopher Samba’s header off the line from Esteban Granero’s corner.
United immediately counterattack and a swift move ended with Cesar producing a fingertip save to keep out Van Persie’s cushioned volley after the Dutchman latched on to a cross from Rafael.
It wasthe Dutchman’s last real involvement of the afternoon as he was substitute five minutes before the break with a back injury he appeared to pick up in an innocuous collision with a photographer in the build-up to United’s opener.
The action barely picked up in the early stages of the second half and Redknapp responded on the hour mark by bringing on January signing Loic Remy for the injured Zamora.
The Frenchman almost made an immediate impact when he cut in from the left and saw his powerful near-post shot saved by David de Gea in the United goal.
Yet as QPR attacked, the game opened up for United on the counter-attack and Sir Alex Ferguson’s side took advantage 10 minutes from time.
Nani played in Giggs and the 39-year-old used all of his experience to beat the offside trap and slot his finish past Cesar.
Moments later, the Welshman nearly scored a second of the afternoon his mis-hit shot skied into the air and inadvertently hit the crossbar. But by then the result was beyond doubt as United stroll towards the title.
