Charlton's Dennis Rommedahl has warned his team-mates not to underestimate the threat of Ruud van Nistelrooy when Manchester United head to The Valley.
The striker has struggled with form and injury this season, but scored twice against Newcastle in the FA Cup semis.
"Ruud hasn't scored many this year, but he is one of the best in the world," said Danish winger Rommedahl.
"It's the first time in a while he is struggling, but he will get back on track - but hopefully not against us."
Rommedahl, 26, knows the Addicks will be in for a tough examination from the Red Devils on Sunday.
Sir Alex Ferguson's United are looking to keep the pressure on Arsenal in the race for runners-up spot in the Premiership.
"If United play like a team they can be good because they have individuals who are top-level players," Rommedahl said in the Kentish Times.
"They can almost win every game - it doesn't matter who they play.
"It will be difficult. We have to match them and give our all. We play good stuff and of course we have a chance.
"Everything is possible, but you need to play your stuff as well as battling hard."