Manchester United knew what was required. After Manchester City went down at Everton, win against rudderless Reading and their advantage would be 15 points and this would be the scene for a de facto coronation of their 20th title.

Wayne Rooney's first-half strike did the business and, while there are nine games remaining and 27 points to fight for, there is surely no way back for the champions and only one course for United: straight to a crown that will help avenge the heartache of City's triumph last season. If they win their next game – at Sunderland – and City lose (at home to Newcastle United), then it will be set up for the Reds to win the derby on 8 April to take their lead to the humiliating dormie of 21 points with seven games remaining.

Yet Sir Alex Ferguson, the arch-winner, was hardly in triumphant mood. "You can [say] what you like, you don't get points or medals for complacency and we won't be," he said.

It was apt that Rio Ferdinand, back in the England reckoning, should take centre stage to create Rooney's goal. The 34-year-old's surge-and-dribble that held off Garath McCleary was the conjuring of a moment from an earlier Ferdinand vintage, when the legs were still youthful and there was no chronic back condition to manage.

Ferguson said: "He broke into the midfield very well. He was always good at that, doesn't do it as much as he used to of course but today it really paid for us."

At the right moment the defender laid the ball off to Rooney, who set himself, then left fly with a finish that benefited from a deflection off Alex Pearce to beat Stuart Taylor and make it 1-0.

This was the score that United's domination deserved. Earlier, it had also been Ferdinand who swept a 50-yard diagonal that fell sweetly into Ashley Young's path down the left corridor. He cut inside on to his right foot to bend a shot that beat Taylor but went narrowly wide.

Rooney, whose strike took him to 197 goals for United, popped up on the right to curl in a cross tinged with quality that forced Reading to scramble clear: the ball took a single bounce 25 yards out then Danny Welbeck blazed a shot that was always rising too high.

After seeing the result at Goodison Park, United had set out to do a professional job with Ferguson fielding a side that showed eight changes from the 2-2 draw with Chelsea in the FA Cup. David de Gea, Rooney and Ferdinand were the only survivors as the manager decided that the challenge of playing the second-bottom team could allow him to freshen the XI up.

The talk around Old Trafford this week featured how mental tiredness was the defining factor in the Chelsea result. United had been two goals up before ending the quarter-final relieved to still be in the Cup with Ferguson arguing the effect of being knocked out of the Champions League by Real Madrid was felt.

Eamonn Dolan, the head of Reading's academy who has taken over on a temporary basis from the sacked Brian McDermott, spent the first half standing in the rain in the technical area. What he saw was Reading come close from a Hal Robson-Kanu 25-yard effort that went the wrong side of De Gea's right post and not much else.

Dolan will have brightened at the action at the start of the second half. Nicky Shorey swung a corner in from the right quadrant and Lee Mason, a Friday afternoon replacement for the injured Mark Clattenburg, turned down a decent penalty claim after Nemanja Vidic appeared to push over Adrian Mariappa. Dolan said: "It was a clear penalty but I think the referee thought I was on work experience."