Fulham 3 Liverpool 1
While the 2-0 victory against United had Liverpool fans convinced they were back in the title race, defeat at Craven Cottage was their fifth in the league this season and another painful reminder of how reliant they are on Steven Gerrard and Fernando Torres.
Gerrard missed the match through injury and after Torres had been substituted, Benitez's men were exposed once again as Erik Nevland won it for Fulham with 15 minutes to spare.
Earlier, Bobby Zamora had given Roy Hodgson's men the lead only for Torres to level it for Liverpool, who saw Philipp Degen and Jamie Carragher sent off late on.
Beating United last Sunday sparked what seemed to be a revival at Anfield but it was back to the drawing board for Benitez as Fulham ran riot.
After the Carling Cup disappointment, it was back to Premier League duties for Liverpool and yet more misery as the red mist descended and their title dreams up in smoke.
Zamora almost opened the scoring early on but he couldn't reach Clint Dempsey's through ball, while Torres was similarly disappointed when Lucas failed to find him on the edge of the box.
It wasn't long before Zamora was celebrating, however. Minutes after Yossi Benayoun cracked the crossbar for Liverpool, Fulham striker Zamora met Damien Duff's cross from the right and coolly slotted the ball past Pepe Reina to stun the travelling support at Craven Cottage.
Once again, the absence of talismanic captain Gerrard seemed to deflate Liverpool and while Benitez is quick to dismiss claims he relies too heavily on the England midfielder, his absence was telling.
Alberto Aquilani was also missing with a virus while Andriy Voronin cut a disconsolate figure as he struggled to provide an adequate partner for Torres.
It was just as well the sublime Spaniard picked up where he left off against United last Sunday. Just when Fulham thought they had engineered a surprise half-time lead, Torres' superb volley nestled into the far corner.
Zoltan Gera and Erik were introduced at the interval and both combined to deadly effect. Winger Gera found the former Manchester United striker in the area and the Norwegian expertly flicked home to send Craven Cottage into delirium with 15 minutes remaining.
Liverpool's hopes to get back into the game were dead-and-buried in the space of four minutes. First, with 12 minutes on the clock and hopes of an equaliser high, Degen was dismissed for a lunge on Dempsey and then Carragher hauled Zamora down and had to go as he was the last man.
Fulham expertly made their advantage count and added a third when Nevland found Dempsey to slot in a third.