It ended 6-5 on penalties following a late Alexandre Lacazette equaliser to ensure it ended Arsenal 1-1 Chelsea in normal time in Dublin.
Check out the highlights above, and you can read on for the four things you ought to know after Wednesday night's display in the Aviva Stadium.
Guendouzi makes us tick
Matteo Guendouzi has only been with us a matter of weeks but he’s already becoming a central figure in the midfield. The 19-year-old started in a deeper midfield role in Dublin and dictated the tempo of our game from there. He quickened the pace when he got on the ball outside the box and spread play with sweeping long passes to the left and right. Another very promising performance from the French teenager.
Petr the penalty king
Petr Cech took a while to save his first penalty for us but now the spot-kick saves are coming thick and fast. The Czech goalkeeper denied Troy Deeney of Watford at the Emirates in March, saved a penalty in the shoot-out against Atletico Madrid in Singapore and made it four in four months or so by thwarting Alvaro Morata and Rueben Loftus-Cheek in Dublin. Oh, and he kept us in the game in the first half with decisive saves from Cesc Fabregas, Morata again, and youngster Callum Hudson-Odoi.
A fluid formation
While Guendouzi sat deeper, Mohamed Elneny and Emile Smith Rowe started the match to the side of him and in slightly more advanced roles. That left Henrikh Mkhitaryan and Mesut Ozil to switch flanks behind centre forward Pierre-Emerick Aubameyang. As the first half wore on it became more of a 4-2-3-1 with Elneny playing closer to Guendouzi.
Hector looks a threat
Hector Bellerin got into advanced positions time and time again, giving Marcos Alonso a problem all night. Our right back was a regular outlet for Guendouzi’s raking passes and linked up well with Mkhitaryan. Hector’s pace and well-timed runs got him in behind Alonso, and one teasing cross was spilled by Willy Caballero into the path of Sead Kolasinac - but the Bosnian took too long.
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