It was another night when Manchester United demonstrated they are not in the mood to relinquish their grip on their Premier League championship trophy and reminded us of the resolve and competitive spirit that authentic champions tend to display when the pressure is close to intolerable.

For long spells Sir Alex Ferguson's team had looked strangely bereft of ideas. They had not taken enough care of the ball and, as the game entered its closing stages, Manchester City were being encouraged to believe their own situation was not, perhaps, as irretrievable as it had looked at the weekend.

But then, how many times have United frayed the nerves of their supporters and then delivered the goals that provide a devastating reminder of their credentials? Antonio Valencia and Ashley Young both scored in the last nine minutes and it has taken the champions five-points clear of Roberto Mancini's side at the top of the table, with seven games to go.

There has been a ten-point swing in four weeks and, from here, it is difficult to believe a team with this title experience will crumple. Their next three games – QPR, Wigan and Aston Villa – are all against teams from the bottom six.

When a side is in a relegation battle it can make them obdurate opponents, as Blackburn demonstrated before slipping back into the bottom three because their goal difference is now worse than QPR's. Yet these are not generally moments when United lose their way.

City, in contrast, have won only one of their last four league fixtures. They looked desperately short during a grumpy, dishevelled performance against Sunderland on Saturday, and United's supporters revelled in a form of malicious pleasure. "City's cracking up," they sang.

It had been a strange night because, for long spells, it was rare to see United have so much possession and so little penetration. Wayne Rooney never looks particularly happy when he is shunted to the left, while Javier Hernández flickered only occasionally. Valencia was a constant menace on the right but it had needed a string of exemplary saves from David de Gea, their renascent goalkeeper, to keep out a Blackburn side that gained in confidence and were the more dangerous side at times in the second half.

Then, on 81 minutes, Valencia advanced from the wing, cut inside and the Blackburn left-back, Martin Olsson, backed off. Valencia is increasingly emerging as United's key player in this title race and the extraordinary diagonal shot from his right boot was a stunning combination of power and precision. It flew past Paul Robinson in the Blackburn goal and it was almost insulting when a television reporter asked him afterwards if he had meant it.

Mancini had accepted at the weekend that if United won here and then beat QPR at Old Trafford on Saturday the title race would be "finished." In the immediate aftermath of the 3-3 draw with Sunderland he had also predicted United would manage only a draw, even offering a bet to anyone who disagreed. Perhaps the City manager was aware they had won only two of their previous 12 visits to Ewood Park. Or maybe it was an attempt something that could be lumped in the mind-games bracket. Either way, he didn't sound terribly convincing at the time.

Valencia's goal broke Blackburn just as they were daring to believe they might actually be capable of following up December's 3-2 victory at Old Trafford with the most improbable double of the season. Five minutes later, Valencia squared the ball into the path of Ashley Young, a 79th-minute replacement for Paul Scholes. Young took a touch to control the pass, spun and turned a precise shot inside the left post.

As has been the case so often this season, there was still the sense of a United team at least one or two notches below their best. In terms of possession, however, they probably deserved the win. A pattern was quickly established whereby long spells of the game were spent in the Rovers half. It was just that they did not always play with the wit to get behind the home defence.

There were moments of vulnerability, too. The first half was a peculiar one because Blackburn were camped inside their own half for much of it but still contributed the three most illuminating pieces of drama. These were the moments when De Gea excelled. Since returning to the team, the Spaniard has been exceptional and there were three spectacular saves in succession.

Junior Hoilett was denied with a stretching, one-handed dive and Grant Hanley's header was turned away from just under the crossbar. The finest of the lot, however, was in between when Marcus Olsson speared a left-foot shot towards the top corner and De Gea turned it away with a twisting, full-length dive. It was probably the outstanding performance of a helterskelter first season in England and he deserved the loud, sustained serenading from the boisterous away following.

This was United's seventh win in a row and their tenth in 11 games since losing back-to-back matches against Blackburn and Newcastle. Late on, Ferguson also heard his name being sung and his reaction told its own story.

The request was for a wave; what they got instead was a fist-pumping, arms-above-the-head victory salute.