Kenny Miller admits Rangers will need to improve from their weekend win at Hamilton if they are to shock Man Utd in the Champions League.
The Scotland striker came off the bench to net his seventh goal of the season to secure a last-gasp 2-1 victory over Hamilton at New Douglas Park on Saturday.
The 30-year-old was rested following his international exploits for Scotland, where he grabbed another crucial goal against Liechtenstein.
Miller knows they cannot afford to play below their best when they face Sir Alex Ferguson's side at Old Trafford on Tuesday.
"We'll be playing one of the best teams in the world, so we're going to really have to up it," said Miller.
"If you ask the manager or any of our coaches, they'll tell you they're not happy with our level of performances so far in the first three or four games of the season.
Bit of luck"You have to work your socks off for the 90 or 95 minutes and there's no doubt you have to carry a bit of luck along the way as well.
"You can defend as good as you want for the majority of the game, but they're always going to create a chance in the match given the standard of player they have.
"It's a level that everyone in the dressing room wants to be playing at and it doesn't come any bigger than playing Man United at Old Trafford.
"There's no doubt it'll be a really tough game, but we know that, if we can go out and play our game, we'll have a chance of getting a result."
Miller is expected to start in the lone striker's role he knows so well from his international career and from playing under Walter Smith at Ibrox.
And he is confident Rangers can produce some good football despite the cautious approach.
"The manager will obviously decide what way he wants to go and whatever he decides will be best for the team to set us out to get the right result," added Miller.
"If he decides to go 4-5-1, it is nothing new to us as we are used to it and we played some great stuff in the majority of games in pre-season using that system."