Rooney’s post-match comments underlined a gulf in class between the two teams this season, with the balance of power swinging back towards a Liverpool side transformed by Brendan Rodgers from mid-table underachievers into title contenders.
United, shockingly for their fans, seem to be heading in the opposite direction – at least in the short term.
The mauling United suffered at the hands of their bitter rivals actually flattered David Moyes’s men.
It is difficult to fathom how a team that won their 20th league title under Alex Ferguson last season have struggled under his successor Moyes. But the reasons for United’s spectacular fall from grace are complex.
Too many players in the squad appear to have reached the summit of their careers last season.
The partnership of Rio Ferdinand and Nemanja Vidic, once the defensive pillars who made United’s rivals in England and Europe green with envy, has come to an end with the latter heading to Inter Milan and the former’s future at Old Trafford uncertain at best.
More surprisingly, striker Robin Van Persie looks a pale shadow of the player whose goals propelled United to the Premier League’s pinnacle last term and his tepid performances have raised question marks over his ability to lead the line beyond this season.
Van Persie criticised his team mates for moving into his space and not getting the ball enough to him after a 2-0 first-leg Champions League defeat by Olympiakos Piraeus, but if they did it is because his poor movement off the ball and lack of cutting edge in big games has been palpably clear.
Rooney, often asked to operate in a dual role of a forward and a midfield workhorse whenever Van Persie is deployed as the lone striker, seems to thrive on his own up front when the Dutchman is sidelined for one reason or another and Moyes is forced to give Danny Welbeck a start.
Moyes, handpicked by his compatriot Ferguson to take over the reins on a six-year contract, seems reluctant to play Mexico striker Javier Hernandez while Welbeck has been used sparingly and mostly out of position.
Expensive acquisition Marouane Fellaini, his former Everton protégé, still looks like a bewildered schoolboy in a United shirt while speculation that Moyes made a futile bid last week to lure Paul Pogba back to Old Trafford suggests that record signing Juan Mata may be more suited to playing further upfield than a playmaker United are still craving for.
A looming Champions League exit on Wednesday is still unlikely to force the board’s hand as Old Trafford’s echelons of power will probably feel they have to give Moyes at least another season to get a grip on things, having backed Ferguson’s choice to name the fellow Glaswegian as his successor.
But even a Champions League comeback in the return leg against Olympiakos and United’s passage into the competition’s last eight is unlikely to be more than a flash in the pan this term unless they can somehow squeeze through to the May 24 final in Lisbon.
Judging by their current form, United will need to produce something very special if they are to get past some of Europe’s heavyweights who now look well and truly out of their league.
(editing by Justin Palmer)