The Red Devils, and manager Louis van Gaal, have come in for more criticism from fans and former players following their limp display in Thursday night's Europa League tie at Liverpool.
Paul Scholes branded them a "shambles" and fellow BT Sport pundit Rio Ferdinand accused them of lacking fight following the 2-0 first-leg defeat.
West Ham currently sit a place above United in fifth in the Barclays Premier League and are full of confidence following back-to-back wins over Tottenham and Everton.
But Bilic knows Van Gaal's side have bounced back from setbacks before this season and claims it would be "suicidal" for his team to take their hosts lightly.
"Thursday night is not a game that you can take as normal for Manchester United," he said.
"It was Liverpool away, it was very intimidating, and it was one isolated game
Unfortunately we are expecting a better Manchester United than that.
"I watched (the criticism) and it's not the first time, to be fair, but when you are manager of Manchester United you have to win every game, so it's really hard for Van Gaal.
"But it was the same situation when they lost against FC Midtjylland
There was lots of criticism, but after that they put in a great performance against Arsenal
They are capable of doing that again.
"They are like a wounded lion, they have a massive game against us
It's going to be very difficult but are we confident? Yes of course we are confident, but not because Manchester United didn't play well
We are confident because we are playing well.
"But it would be dangerous, suicidal, if we approach the game like 'they are playing badly, we are playing well, and we are going to cruise it'
No way we will do that."
Bilic can welcome back defender Joey O'Brien and wingers Victor Moses and Enner Valencia from injury for the Old Trafford clash.
Source : PA
Source: PA