West Ham boss Slaven Bilic says the FA Cup is a priority.
Standing between the Hammers and a place in the quarter-finals are a Blackburn Rovers side 18th in the Championship.
"It will be a big test for us," said Bilic. "They are not having a great season but they are solid, they don't concede many goals.
"No matter who you play, you are playing for the quarter-finals and that's where we want to be. The win against Liverpool will have more value if we progress in the cup.
"We have rested a few players this week and I think we are well prepared for the game.
"We'll take nothing for granted, it will be a very difficult game but we are a Premier League side, we are having a good season so far and I will be really disappointed if we don't go through."