Ki Sung-yueng was the hero as the Mackems dumped Chelsea out of the Capital One Cup with a 2-1 win after extra-time to book a place in the semi-finals.
The South Korea international, on loan at the Stadium of Light from Swansea, struck in the 118th minute to complete a famous victory and end Jose Mourinho's hopes of winning the trophy which gave him his first honour during his previous spell at Stamford Bridge.
Lee Cattermole's own goal looked to have sent Chelsea through to the last four until substitute Fabio Borini struck with just two minutes of normal time remaining to send the tie into extra time.
Indeed, the Italian might have won it in stoppage time had it not been for Gary Cahill's desperate challenge with the Black Cats mounting a late charge.
Edin Dzeko pressed his case for a regular run in the Manchester City side with two goals in a comfortable 3-1 win at Leicester.
With top scorer Sergio Aguero facing at least a month out, Dzeko took his chance to shine at the King Power Stadium by netting twice after Aleksandar Kolarov opened the scoring with a free-kick.
Leicester, third in the Sky Bet Championship, had gone into the game with confidence but were outclassed by a City side showing eight changes but finished strongly and netted through a deflected Lloyd Dyer consolation.