Hernandez wriggled away from Jose Enrique to touch home Wayne Rooney’s corner. The Mexican’s first goal of the campaign came so early in the second-half, United manager David Moyes had barely got beyond the penalty area in his walk to the home dug-out.
It meant it was easy to spot the Scot’s celebration, at a strike that should at least quell some of the angst that built up following that awful hammering at Manchester City four days ago.
It was a moment shared by defender Jonny Evans who said the red Devils will be taking the competition very seriously.
“We want to win it,” he said. “It was the first trophy I won and it was a great feeling to win it then.
“It’s a competition we want to win, we will be taking it seriously.”
Evans added: “I think the fans enjoyed it, we certainly enjoyed it.
“It was a hard game, Liverpool have been playing expansive football.
“I am just glad we got the goal after half-time and held on.
“They put out a strong team. There were a lot of lads out there who haven’t had a lot of football and were getting a bit tired towards the end.”
Indeed, United’s performance was not perfect and the game marked the return of Luis Suarez following a 10-match suspension. The Uruguayan came close to levelling when his vicious free-kick struck the bar with David De Gea beaten.
De Gea had only just repelled Victor Moses’ powerful diving header but the hosts had chances to sew up the contest too, with Simon Mignolet producing a couple of excellent saves to deny Rooney.
And after bravely riding the hefty punches landed on him at the Etihad Stadium, Moyes was probably not that bothered about the actual scoreline anyway, just the much-needed victory against one of England’s biggest clubs, and United’s greatest rivals.
It was hardly a surprise Suarez started either.
After all, when you have spent so long out and are desperately in need of match fitness, there is little to be gained by kicking your heels on the bench watching others do what you are paid so much for.
Perhaps understandably though, the Uruguayan was not quite on top form.
He was caught on his heels slightly when Steven Gerrard rolled an inviting pass into his path, which allowed Rafael to slide back and clear.
And when Enrique’s curling cross dropped over Jonny Evans’ head, Suarez’s first touch was just too long so De Gea was able to slide out to bravely block his second. He did supply the through ball that ended with Daniel Sturridge toe-poking wide, however.
United started with intent. Nani and Shinji Kagawa were particularly lively, whilst stand-in captain Rooney buzzed around with menace.
However, with the exception of a Nani effort that was deflected wide, all that early pressure fizzled out and it wasn’t until much later in the half United started to force the pace again.
Some kind of relief was required. And it arrived through Hernandez’s goal a minute after the re-start with the deftest of touches after peeling off Enrique.
Liverpool responded to the setback with impressive vigour. Indeed, they should have been level when United’s defence got themselves in a muddle attempting to subdue a joint raid involving Suarez and Sturridge and succeeded only in presenting Jordan Henderson with a shooting chance.
The England man had enough time to do better than merely drag a disappointing shot wide. And he knew it.
So unhappy was Gerrard with that waste of possession that he very publicly rebuked his team-mate, who kept his head down as he ran back to his defensive station. It was the prelude to a thrilling finish, in which Moses, Suarez and Rooney, twice, all came close.
MANCHESTER UNITED: De Gea, Rafael, Evans, Smalling, Buttner, Jones, Rooney, Giggs, Nani (Welbeck 90’), Kagawa (Januzaj 73’), Hernandez (Carrick 74’).
LIVERPOOL: Mignolet, Toure, Sakho, Skrtel, Jose Enrique, Gerrard, Moses (Sterling 82’), Henderson, Lucas (Kelly 67’), Suarez, Sturridge.
Referee: Mark Clattenburg