Leicester boss Claudio Ranieri hopes the FA Cup win over Derby will aide the champions' relegation fight in the Premier League.
A much-changed Leicester team, with Ahmed Musa the only survivor from the 3-0 defeat to Manchester United at the weekend, dug deep on Wednesday night to overcome Championship promotion hopefuls Derby 3-1 after extra time.
Wilfred Ndidi and Demarai Gray scored in the additional half an hour to set up a fifth round trip to Millwall and give Leicester a first taste of success in six matches ahead of Sunday's crucial clash at fellow strugglers Swansea.