Aguero has not played since 27 November because of a groin injury, while De Bruyne returned from knee injury on Saturday after a six-week layoff.
In total, Guardiola has made eight changes from the side that started Saturday’s 3-1 win over Everton in the Premier League.
City, the holders, are looking to book a place in the semi-finals of a competition we have won on five occasions, including three times in the past five years.
Muric, Walker, Stones, Otamendi, Zinchenko, Eric Garcia, De Bruyne, Foden, Diaz, Mahrez, Aguero
Subs: Ederson, Sterling, Gundogan, Delph, Jesus, Sandler, Nmecha
It looks like the usual 4-3-3 formation, with Garcia at centre-half alongside Nicolas Otamendi. If that is correct, it’s likely John Stones will operate in the holding midfield role with De Bruyne and Foden just ahead of him.
Diaz and Riyad Mahrez will look to provide quality in wide areas, with Aguero playing through the middle.
Leicester have been eliminated from all four of their previous League Cup meetings with Manchester City, including a penalty shootout defeat in this round last season.
Manchester City have gone on to win the League Cup the last two times they've faced Leicester in the League Cup - knocking them out at the quarter-final stage in both 2013-14 and 2017-18.
This is only the second time Leicester have faced the holders of the League Cup, with the Foxes losing 4-3 against Chelsea in the 2007-08 campaign.
Leicester are looking to reach the League Cup semi-finals for the first time since 1999-00, when they went on to win the competition.
Manchester City haven't been eliminated at the quarter-final stage of the League Cup since 2007-08, when they lost to eventual winners Spurs. They've progressed the last five times they've reached this stage.
Leicester are yet to concede a goal in this season's League Cup.
Leicester's last two League Cup games have been decided on penalties - only Liverpool and Stoke in 2015-16 and Cardiff in 2011-12 have had three games go to penalties in a single edition of the competition.
Leicester's Kelechi Iheanacho has been involved in seven goals in his nine League Cup matches with Leicester and Man City combined (4 goals, 3 assists).