Liverpool is still six points behind EPL leader Chelsea and trails Lyon and Fiorentina in its Champions League group, but the Reds got a boost with their win over United without Liverpool's injured star Steven Gerrard.
"We needed to win for the confidence, so I think it will be a big boost for the team," Benitez said. "All the players didn't want to lose. They wanted to show character and this was the perfect response. It was against a good team so the fans are delighted and then you can see all the players feel the same way. It has to be positive. Hopefully this will be a turning point. If we can keep the momentum I am sure we have a good team and can win some games in a row."
Even without Gerrard, Liverpool won the game in midfield, where Javier Mascherano, Lucas and Fabio Aurelio were outstanding.
Like Gerrard, Spaniard Fernando Torres has been battling a groin injury, but he celebrated his return with a well-taken goal to give Liverpool the lead in the 65th minute.
David Ngogadded an insurance goal late in the game after Nemanja Vidic (red card for a professional foul on Dirk Kuyt) and Mascherano (second yellow card) has been sent off, reducing both teams to 10 players.
The loss was United's first this season in all competitions.
Manchester United manager Sir Alex Ferguson admitted his team had been outplayed but he was confident his players will bounce back.
"Last year we lost 4-1 at home to Liverpool, got hold of the bit again and went on to win the league and that is our challenge," he said.