"You never know what can happen in football but we know how much experience and quality United have in their squad."
It was Liverpool's biggest win at their fierce rivals since 1936 and they closed the gap at the top of the league to four points, although United also have a game in hand.
"We have shown the way," said Benitez. "United have been playing with so much confidence. At least people will now see that they can lose.
"The message is there for everyone. In attack they are fantastic. You can see the quality they have. But in defence they have some weaknesses and we tried to exploit them."
He also hailed the influence of Torres and Gerrard on the performance at Old Trafford.
"Torres and Gerrard are obviously key players for us," admitted Benitez. "When they are on the pitch the rest of the team has more confidence."
Gerrard praises 'magic' Torres
Because of injuries to the formidable pair, they have only played together nine times in the league.
But captain Gerrard believes if Torres can remain fit until the end of the season, the title race will go down to the wire.
He told BBC Sport: "He's magic. I know I'm going to be biased but I don't think that anyone will argue against me that he's the best striker in the world.
"If we keep him fit from now to the end of the season, it's going to be an exciting finish.
"I believe that If we'd had him fit for more games we'd be closer or even in front of United."
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