Cristiano Ronaldo answered Sir Alex Ferguson's title SOS to send Manchester United four points clear at the Premiership summit.

Goalless at half-time against unfancied Wigan, with Wayne Rooney struggling and five senior stars left out, the Red Devils looked set to be thwarted in their attempt to take maximum advantage of Chelsea's failure to beat Reading.

But, for the second time in four days, Ronaldo came to the rescue, following up his two-goal salvo at Aston Villa by bagging another brace, the crucial opener coming with his first touch just 69 seconds after his arrival.

Ronaldo reached double figures for the season when he drilled home the rebound after outstanding Latics keeper Chris Kirkland had saved his 49th-minute penalty and, with Ole Gunnar Solskjaer adding another before the hour mark, United were able to coast to a victory which will only further fuel belief their four-year championship drought will be over in May.

The news which filtered through from Stamford Bridge immediately before the teams emerged from the tunnel came too late to influence Ferguson's selection.

However, the sight of autograph hunters surrounding Rio Ferdinand and Ryan Giggs as they took their seats in the directors' box brought a fleeting thought of the possibility United might waste the unexpected chance they had been presented with.

Ferguson's strategy was easy enough to understand. With Paul Scholes and Nemanja Vidic suspended from United's own encounter with Reading next Saturday, Ferdinand and Giggs were the natural choices to sit out the latest battle between the meek and mighty of the Premiership's extended north-west brigade.

In four victorious meetings with Wigan since the Latics elevation to Premiership status - including a Carling Cup final demolition last February - Ferguson's side have amassed 13 goals to their opponents two.

Yet it did not take long until an unspoken fear gripped Old Trafford that this could be one of ''those' days.

Only six minutes were on the clock when Wes Brown skipped past Emile Heskey, charged to the by-line, then drilled over a cross which invited a far-post finish from Rooney.

Amazingly, the England star fired straight at Kirkland, who then showed lightning reactions to claw the ball away before it bounced over the line.

It was the start of a magnificent first-half display from Kirkland, who was equal to everything United struck at him.

Park Ji-sung, United's most effective attacking performer during the opening period, Mikael Silvestre, Paul Scholes and Ole Gunnar Solskjaer were all denied by Kirkland, although it was Rooney who had all the best chances.

Either side of one long-range effort which fizzed over came two gilt-edged chances, both of which were created by Darren Fletcher.

Inexplicably, Rooney failed to get a touch on the first when he would have been completely clear eight yards out. The England star at least managed to get hold of the second but, after poor initial control, he eventually turned and fired wide.

As the half-time whistle blew, more than a few worried noises rumbled round the stadium. The sight of Ronaldo warming up brought an almost audible sigh of relief and within 15 minutes of second-half action, United knew they would be seeing in the new year as England's top dogs once more.

For, no matter what happens against Reading next weekend, United cannot be ousted from top spot before January 1. And with Ronaldo in this mood, it may be long after that date before Chelsea eventually scramble back to the top, if they manage it at all.

Certainly, Ronaldo appears as important to the Red Devils just now as Didier Drogba is for Jose Mourinho's men.

Aerial ability has hardly been a feature of his time at Old Trafford but the young wide man's height alone marks him out as a powerful penalty box presence and when Scholes drilled over a right-wing corner a minute after the restart, Ronaldo's first touch of the contest was a searing header which flew into the top corner.

Although Kirkland's inspired personal performance continued when he saved Ronaldo's spot-kick after Park had been caught late by Gary Teale in the box, his luck ran out as the rebound rolled back to the winger, who is now adding the finishing touches to his masterful wing play.

Solskjaer clinically finished off another just before the hour mark, which effectively sealed the points, even though Rooney's frustrations continued when he struck the bar late on.

Wigan's belated hunt for a consolation was eventually rewarded when Leighton Baines smashed home an injury-time penalty but the Latics have still to grab a point against any of the big four.

How United hope that run ends at Stamford Bridge on January 13.

Teams

Man Utd Van der Sar, Brown, Vidic, Silvestre,Evra (Heinze 70), Fletcher (Ronaldo 46), O'Shea,Scholes (Richardson 62), Park, Solskjaer, Rooney.

Subs Not Used: Kuszczak, Saha.

Goals: Ronaldo 47, 51, Solskjaer 59.

Wigan Kirkland, Boyce, Jackson, Hall (Skoko 60), Baines,Teale (Cotterill 52), Johansson, Wright, Kilbane, Todorov,Heskey.

Subs Not Used: Pollitt, Landzaat, Cywka.

Goals: Baines 90 pen.

Att: 76,018

Ref: M Riley (W Yorkshire).