Richard Stearman says the Blades must go to Craven Cottage in positive mood on Tuesday evening.
And despite acknowledging Fulham's obvious threat, with the Cottagers unbeaten in the league in 2018, Stearman is optimistic about United's prospects against his former club.
Looking ahead, the defender commented: "Fulham are flying really high and are obviously doing really well. I expect them to be right up and about it come the end of the season.
"It's going to be a very tough game for us, but one where we have to be confident we can pull off a positive result.
"They've got the financial clout, they had a very good base to begin with but they've managed to add quality players to the ranks this season.
"Look at Reading, being in the play-offs the previous season can cause a hangover, but Fulham have regrouped and performed really well this season, excellently of late."
And the experienced performer knows Fulham will have a plethora of attacking options at their disposal, with 17-year-old Ryan Sessegnon in fine form of late.
Stearman added: "Sessegnon actually made the squad a few times when I was there, I think we had to drag him out of school to be honest.
"He was a talent then, but he's come on leaps and bounds since and he's obviously someone we're going to have to stop on Tuesday.
"Ryan's versatile and can play anywhere down that left-hand side. He came through as a left-back, but he is enjoying himself higher up the pitch at the moment and scoring a lot of goals.
"But they have a lot of quality players you can name, we know it will be a real test and a tough game."