Neil Harris has told his Millwall players that their FA Cup tie against Leicester City is “a different level” to their previous Premier League knockouts.
The Lions have already dumped out Bournemouth and Watford and can make it a hat-trick against the reigning Premier League champions.
Leicester are just above the dropzone but have progressed to the last 16 of the Champions League – and go to Sevilla on Wednesday.
It looks likely that Foxes boss Claudio Ranieri will make wholesale changes to his starting line-up with that trip to Spain in mind.
Millwall are unbeaten in 12 matches with five successive clean sheets.
“When people talk positively about us having a chance of beating the Premier League champions it is testament to the form we have been in,” said Harris.
“But Leicester are by far the favourites to win the tie. Every Leicester fan, every member of staff and player will look at it and know if they get past us they are into the quarter-final and have a great chance to reach the semis.
“Leicester should be in the last eight of this competition – they are in the last 16 of the Champions League and won the title last season. They recruited players to be in the top-six again – not the bottom.
“It will be a real tough ask for us to repeat the performances against Bournemouth and Watford but it’s a one-off game and my players can rise to the occasion.
“The atmosphere will be electric and hostile – they won’t be welcome. If we can catch Leicester on an off day then we’ve certainly got the opportunity for the biggest giant-killing so far.”
Leicester have won just one of their last 15 away matches – drawing five of them.
“It is not as good as their home form but there are various factors for that,” said Harris. “This is the fifth round of the FA Cup and that goes out of the window. They won at Everton and drew at Derby. They have won away from home in Europe. They’ve stuttered in the league – but maybe it is a cup season for them.
“Leicester is different to what we have done before. They are Premier League champions and they earned that by rights. They have spent a lot of money in the summer – this is a different level for us because of what they’ve achieved in the last 18 months.”
Ranieri has already stated that Leicester’s slide into the relegation dogfight has shifted their priorities.
He said: “At this moment our aim is to stay in the Premier League. The FA Cup and Champions League is something good – but it is not our focus.”