Manchester United manager Ole Gunnar Solskjaer handed his players a warning after their FA Cup third round victory against Reading at Old Trafford.
First half goals from Juan Mata and Romelu Lukaku eased United into the fourth round of the FA Cup after a 2-0 triumph, yet a much-changed team struggled to find their rhythm throughout.
After making nine changes to the line-up that handed Solskjaer his fourth straight win as United manager at Newcastle last Wednesday, the Norwegian admitted his revamped side were blow par in front of a muted Old Trafford crowd - and that they will come away empty-handed against Spurs if that performance is repeated next weekend.
"If that performance is repeated at Wembley against Spurs, we will not come out with any points," declared Solskjaer, who became the first United manager to win his first five matches in charge with this latest victory.
"The result may have been better than the performance today. We are delighted we are through and that we have a clean sheet, but they made it tough for us.
"We analysed them, we knew they were going to come and play and I have to say, they played well. They have some quality players and they made us work hard to get possession and when we got the ball we were too wasteful, we know that. We have spoken about loads of things to improve on.
"In truth, probably I made it tough for us. When you make nine changes, it is never easy for a team that has never played together to find fluency. We are through, that's good, but clearly we can play better than that.
"We are learning a lot every single day, every game we play together and there are loads of things for us to improve on.
"Spurs at Wembley is a proper test in our next match. That will give me more of a reference where we are against the top boys."
A limping Alexis Sanchez was among those withdrawn in the second half, but Solskjaer was hopeful he could be fit to face Tottenham.
"I hope it's not going to be too bad," he added. "It's the same hamstring that he's been having trouble with but we'll see. Hopefully he'll be OK for next weekend."
Republic of Ireland hopeful Liam Kelly was among the brighter sparks in an encouraging performance from Championship strugglers Reading, with their new manager Jose Gomes now hoping to add to his options in the transfer window.
"We cannot find connections between the performance and the result. I'm very proud of what my players did today," said the Reading boss.
"It's not easy to come from the situation that we are in and show the intensity and courage and positive ideas.
"We were lacking a killer instinct. I'm sure that if we catch the good things we did today against very strong players, my players could do it. They showed they were able to play. This is a strong place to look to the future.
"Now I think we should bring in four or five players in the transfer window. We just need to find a loan player who can help who is better than the players that we have."
Ole Gunnar Solskjaer's winning start to life at the Manchester United helm continued but the FA Cup third-round triumph against embattled Reading was the caretaker manager's most unconvincing performance to date.