The Foxes enter the showdown on the back of a 1-0 Premier League defeat to Fulham, while the hosts' struggles continued with a 1-0 loss to Stevenage on Monday.
Match preview
Seemingly boasting a one-way ticket to relegation from League Two, Gillingham remain in deep trouble under the tutelage of Neil Harris, who took full responsibility for their latest loss to Stevenage in a one-goal beating on Monday night.
Carl Piergianni's header on the 23-minute mark settled the contest between the two sides, who were involved in a heated clash at the break amid a "frank exchange of views" as described by Harris, whose team remain rooted to the foot of the League Two standings with just 14 points to their name.
Entering the third round of the FA Cup on the back of four successive losses in all competitions, Gillingham needed replays to overcome Fylde and Dagenham & Redbridge in the opening rounds of the tournament, reaching stage three for the first time since losing at this point to West Ham United in 2019-20.
It will come as little surprise to learn that the Gills have never gone all the way in the FA Cup, but only three of their last 10 home games in all tournaments have ended in defeat, and the Priestfield faithful will welcome any small glimmer of hope that comes their way.
Fewer than two years ago, Leicester fans rejoiced in Youri Tielemans's sensational winner against Chelsea to clinch FA Cup glory in front of their ardent fans. Fast-forward to January 2023, and the Foxes' position is all the more precarious.
The visitors' Premier League clash with Fulham on Tuesday night was to be decided by just the one goal rather than a pair of Wout Faes own goals, but Brendan Rodgers's crop still ended up on the losing side as Aleksandar Mitrovic struck with 17 minutes on the clock.
Had it not been for the steadfast efforts of Bernd Leno, Leicester could have been celebrating a different result at the King Power, but three successive defeats since the resumption of club football has left the visitors 13th in the top-flight rankings and just two points from being dragged into a relegation scrap.
The Foxes' FA Cup defence ended in humiliating circumstances last season with a 4-1 defeat to Nottingham Forest in the fourth round, but they have only suffered one third-round elimination in five of the last six editions, going down to Newport County in 2018-19.
Saturday's game will mark the sixth meeting between Gillingham and Leicester in any competition, with the Foxes winning four of those previous clashes, including in January 2005 where Dion Dublin scored in a 2-0 Championship triumph.
Gillingham FA Cup form:
D
W
D
W
Gillingham form (all competitions):
L
W
L
L
L
L
Leicester City form (all competitions):
W
W
W
L
L
L
Team News
Gillingham lost defender Elkan Baggott to a long-standing ankle issue just before the clash with Stevenage - the Indonesia international started the warm-up before having to pull out after aggravating the problem.
Will Wright and Max Ehmer should therefore form an untouched centre-back pairing for the hosts, who could soon see Haji Mnoga return to parent club Portsmouth from his disappointing loan spell.
Left-back Ryan Law's participation is also up in the air as Plymouth Argyle weigh up whether to recall the 23-year-old in January as well.
As for Leicester, the brimming King Power treatment room has welcomed its newest occupant in Boubakary Soumare, who only lasted eight minutes of the defeat to Fulham before suffering a hamstring strain.
Soumare joins the likes of James Maddison, Jonny Evans, Dennis Praet, Patson Daka, Ryan Bertrand, Ricardo Pereira, James Justin and Kiernan Dewsbury-Hall in the medical bay, but Rodgers should make a multitude of changes in any case.
Daniel Iversen, Nampalys Mendy and Kelechi Iheanacho are among those who should be handed opportunities to impress, but Caglar Soyuncu may not be considered for any minutes ahead of a proposed switch to Atletico Madrid.
Gillingham possible starting lineup:
Morris; McKenzie, Wright, Ehmer, Tutonda; Jeffries, Williams, O'Keefe, MacDonald; Adelakun, Mandron
Leicester City possible starting lineup:
Iversen; Castagne, Amartey, Vestergaard, Thomas; Mendy, Tielemans; Albrighton, McAteer, Barnes; Iheanacho
We say: Gillingham 0-3 Leicester City
Even with several first-team stars likely to be rested and myriad more in the medical bay, Leicester should still prove far too strong for an out-of-sorts Gills team here.