London - Manchester City boss Pep Guardiola enjoyed a far more comfortable evening despite also ringing the changes as England under-19 international Phil Foden shone in a 3-0 win at League One Oxford.
The visitors dominated throughout but had just the one goal to show for it before half-time as Gabriel Jesus headed home from close range.
Fresh from his first two goals for the club at Cardiff on Saturday, Riyad Mahrez then thrashed home a second on the counter-attack 12 minutes from time.
And Foden rounded off a fine individual display with his first senior goal for the club in stoppage time.
Another League One side Burton provided the other upset of the night by coming from behind to beat Premier League Burnley 2-1.
The Clarets went in front through Kevin Long, but Burton reached the fourth round for the first time in their history as Liam Boyce levelled before Jamie Allen poked home the winner.
The only all Premier League tie of the night saw Leicester edge out in-form Wolves 3-1 on penalties after a 0-0 draw thanks to three shootout saves from Danny Ward.
Fulham's strength in depth was in evidence as they swept aside Championship Millwall 3-1 at The Den despite making 10 changes.
Crystal Palace proved too strong for West Brom as an Andros Townsend double and Patrick Van Aanholt secured a 3-0 win at the Hawthorns.
Bournemouth struck late through Callum Wilson to squeeze past Blackburn 3-2 after blowing a two-goal lead in the second-half.
Jordan Rhodes's hat-trick ensured Norwich saw off a second-half fightback from Wycombe to edge through 4-3.
Middlesbrough progressed 4-3 on penalties after a 2-2 draw with Preston and League One Blackpool beat Championship strugglers QPR 2-0.