Republic of Ireland under-21 international Will Smallbone missed a vital penalty to allow Chelsea progress to the quarter-finals of the Carabao Cup.
They beat Southampton 4-3 in last night's shootout - having knocked out Aston Villa on spot-kicks in the previous round.
It adds to an already hectic fixture list for the European champions.
But boss Thomas Tuchel tells Sky Sports News, he wouldn't have it any other way.
Arsenal boss Mikel Arteta says he asked his squad players to take their chance to impress - and feels they grabbed it in last night's 2-nil League Cup win against Leeds.
Calum Chambers came off the bench to score seconds after coming on in the second-half, before Eddie Nketiah sealed their quarter-final spot.
Arteta says they delivered exactly what he wanted.
Former Ireland winger Aiden McGeady scored the first penalty in Sunderland's shoot-out win away to QPR.
The quarter-final line-up will be completed tonight.
Holders Manchester City are away to West Ham.
Liverpool travel to Championship side Preston.
Brighton manager Graham Potter has urged Aaron Connolly to seize his chance in tonight's trip to Leicester.
Burnley entertain Tottenham, and Stoke play Brentford.
