The Gunners looked to be heading back to London with a serviceable 2-1 defeat after having Sokratis Papastathopoulos sent off in the first half, but Sarr's dramatic late goal put daylight between the sides to leave Arsenal seemingly on the brink.

It all started so well for Unai Emery's men when Alex Iwobi's somewhat fortuitous early effort gave them an away goal that may yet prove decisive.

The good feeling did not last as Sokratis was given his marching orders for two yellow-card offences, and Benjamin Bourigeaud netted a stunning equaliser as a result of the second offence.

The home side looked desperate to make the most of its numerical advantage and the pressure paid off, as Monreal deflected a cross into the goal and Sarr rounded off a brilliant performance with an emphatic diving header.