The visitors will enter this contest off the back of a 4-1 victory over Huddersfield Town on New Year's Day, while Millwall recorded a 1-0 win over Bristol City in their last match in the second tier.
Match preview
Millwall stretched their unbeaten run in the Championship to five matches on New Year's Day when they recorded a 1-0 victory over Bristol City, with Shaun Hutchinson netting the winner in the final exchanges.
The Lions have now beaten Queens Park Rangers, Norwich City and Bristol City in their last three matches, which followed back-to-back draws against Stoke City and Huddersfield, with their strong recent run moving them into 15th position in the table on 32 points, 10 points clear of the relegation zone.
Millwall's last loss actually came against Leicester - a 3-2 reverse at the King Power Stadium in the middle of December - but there will be a different feel to this match, as both managers are likely to rest some important players, with the league certainly taking priority.
The London club have never won the FA Cup, but they famously reached the final in 2003-04, suffering a 3-0 defeat to Manchester United in the clash in Cardiff.
Millwall have lost each of their last three fixtures in this competition, meanwhile, and they have been knocked out in the third round in the last two seasons by Crystal Palace and Sheffield United.
Leicester's squad is so incredibly strong that it not a surprise to see them flying high at the top of the Championship table, with the Foxes proving to be comfortably the best side in the division thus far this term.
Enzo Maresca's side have won 21, drawn two and lost three of their 26 league matches this season to collect 65 points, which has left them 10 points ahead of second-placed Ipswich Town and 13 clear of Southampton in third, so it would be a shock if they were not back in the Premier League next season.
The Foxes were 4-1 winners over Huddersfield in the league on January 1, and they are unbeaten since a 1-0 defeat at Middlesbrough on November 11, winning eight of their last 10 matches.
Leicester famously won the FA Cup for the first time in 2020-21, recording a 1-0 victory over Chelsea in the final of the competition, with Youri Tielemans netting the only goal of the contest.
The Foxes have won their last two games against Millwall, meanwhile, but they suffered a 1-0 defeat when the two teams locked horns in the fifth round of the FA Cup in February 2017.
Millwall form (all competitions):
L
D
D
W
W
W
Leicester City form (all competitions):
W
W
W
D
W
W
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Team News
Millwall will again be missing Casper De Norre on Saturday due to a calf problem, while Wes Harding is also expected to be unavailable for selection with a knock.
George Saville is another absentee for the home side this weekend, as the midfielder is serving the second of a two-match suspension.
There have not been any further issues reported from the clash with Bristol City last time out, but head coach Joe Edwards is set to make changes from the side that started on New Year's Day, with Aidomo Emakhu, Kevin Nisbet, Danny McNamara, Joe Bryan and Bartosz Bialkowski set to be among those introduced.
As for Leicester, Jamie Vardy and Kasey McAteer will again be unavailable for selection, with the pair out until later this month, while Kelechi Iheanacho remains a doubt.
Head coach Maresca will also make a number of changes from the clash with Huddersfield last time out, with Conor Coady, Kiernan Dewsbury-Hall, Hamza Choudhury, Marc Albrighton and Callum Doyle all bidding to start.
There should also be a spot between the sticks for Jakub Stolarczyk, while Thomas Cannon struck twice against Huddersfield and should retain his position as the centre-forward.
Millwall possible starting lineup:
Bialkowski; McNamara, Hutchinson, Cooper, Bryan; Honeyman, Mitchell; Emakhu, Flemming, Longman; Nisbet
Leicester City possible starting lineup:
Stolarczyk; Doyle, Vestergaard, Coady, Nelson; Dewsbury-Hall, Choudhury, Winks; Albrighton, Cannon, Mavididi
We say: Millwall 1-2 Leicester City
Both managers will make changes to their strongest sides for this match, but it should still be a very competitive contest. Millwall have home advantage, but Leicester have been so strong this season, and we are backing the visitors to secure their position in the fourth round of the tournament.