When Sir Alex Ferguson suggested this week that Liverpool might lack the necessary experience to stay the pace over the second half of the Premier League season, he touched a raw nerve with Rafael Benitez.
Infuriated, the Liverpool manager responded caustically by claiming that it was, in fact, his Manchester United counterpart who was betraying signs of apprehension as the season heads towards its decisive phase.
Ferguson's demeanour of late has offered little to support that suggestion.
But the Scot readily admits that the champions' margin for error has been curtailed by the unexpected resilience of Liverpool's challenge this season and, in the process, substantially raised the stakes involved in Chelsea's visit on Sunday.
United's two games in hand reduce the significance of the eight-point advantage Liverpool held over the champions as 2009 got underway.
But United can ill afford to see their current momentum stalled by a Chelsea side which arrives at Old Trafford with almost identical concerns and a record of eight wins from their ten away matches this season.
"The games we have in hand gives us the opportunity to close the gap on those clubs at the top," Ferguson said ahead of what will be Chelsea's first visit to Old Trafford under Luiz Felipe Scolari.
"Those two games are at home and it's important we take advantage of that. But the first thing is to win Sunday's game. That's the one that can set us on our way."
For Scolari, a victory would help him to repudiate criticism that he lacks the nous required to make the difference in major matches, an argument that has been fuelled by the Brazilian's failure to secure a win over United, Arsenal or Liverpool since he arrived in England last July.
Given his coaching pedigree, that kind of criticism inevitably causes Scolari to bristle a little.
"I didn't win only the World Cup, I won two Copa Libertadoes and many things in Brazil," he reminded his critics, before endorsing Ferguson's assessment of this encounter as a potentially pivotal meeting.
"We need to win because this is a game that if they take three points it is difficult to recover after," the Brazilian acknowledged.
"If you draw you lose two points and so did the opponent but if you lose it is difficult.
"In our position, we need to think only about winning. We are only four points ahead of them and they have two games in hand. If we don't win it is not in our hands."
Both sides will be close to full strength with John Terry and Michael Ballack, for Chelsea, and United's Patrice Evra all returning from suspensions while Rio Ferdinand has recovered sufficiently from a back problem to make his first start in almost a month.
"You always benefit from having your best players available and Rio's one of the best in the world," said Ferguson, who will have been relieved that he will not have to rely on the inexperienced Jonny Evans at centreback for a match which could see Chelsea deploy both Nicolas Anelka and Didier Drogba in attack.
United had the better of the contest when the two sides met at Stamford Bridge earlier in the season but Salomon Kalou's late equaliser rescued a point for Scolari's men.
Away from home, Chelsea have been far more incisive however, as Ferguson recognised.
"Normally you are talking about Chelsea being unbeaten at home," he said. "But this season it is their away record that has kept them at the top. It is absolutely outstanding."
United's home form has been equally impressive -- seven league wins in succession since Newcastle claimed a point on the opening weekend of the season -- so something will have to give on Sunday.