Dirk Kuyt came off the bench to score a dramatic winner for Liverpool and send the Reds through to the fifth round of the FA Cup at the expense of Man Utd.
Anfield was a cauldron of intense atmosphere as it gave a hostile reception to Utd defender Patrice Evra.
Daniel Agger had given Liverpool a first half lead with a solid header from a corner, but that had been cancelled out shortly before half time when Valencia took advantage of some sloppy defending from Jose Enrique to cross the ball in for Park to equalise.
Kuyt’s goal was simple but clinical. Pepe Reina’s goal kick was flicked on by Andy Carroll, and Kuyt finished expertly and low through De Gea’s legs.
Liverpool: Reina, Enrique, Skrtel, Agger, Kelly, Downing, Carragher (Kuyt 63), Gerrard (Bellamy 72), Maxi (Adam 63), Henderson, Carroll.
Subs not used: Doni, Johnson, Coates, Spearing.
Man Utd: De Gea, Evra, Smalling, Evans, Rafael, Carrick, Park, Scholes (Hernandez 76), Giggs, Valencia, Welbeck.
Subs not used: Ferdinand, Berbatov, Fabio, Lindegaard, Pogba, Keane.
Ref: Mark Halsey