The Gunners led three times in total against a Liverpool side depleted of their regular starters before succumbing to a 5-4 loss on penalties after the tie finished 5-5.
Emery himself fielded a team with 11 changes from the weekend’s disappointing 2-2 draw with Crystal Palace at The Emirates - with the return of forgotten man Mesut Ozil to the starting XI a welcome sight for sore Arsenal eyes.
Ozil himself was hauled off after 65 minutes and Arsenal, who were helped by goals from Martinelli (2), Lucas Torreira, Ainsley Maitland-Niles and Joe Willock, conceded a 93rd-minute equaliser to bring the game to penalties where they eventually fell to defeat thanks to young Irish keeper Caoimhin Kelleher denying Dani Ceballos.
The defeat comes at a bad time for Emery. A string of poor domestic results has seen the Spaniard shorten drastically in the next Premier League manager sacked market.
Having not featured in the top-ten of the betting prior to their defeat to Sheffield United last Monday, Emery now sits agonisingly close to the top of the market, coming in as the third favourite at odds of 7/1 to part ways with his North London employers.
However, ‘The Tinker Man’ - as he’s been dubbed in mainstream media due to his half-time substitution tactics - does not need to worry about getting the chop anytime soon according to ex-Arsenal legend Nigel Winterburn.
He told Gambling.com: "All clubs are looking and analysing what's happening at their club. I've always said that when Unai Emery came in he would get at least two years. Last year it wasn't his team.
"Now he's had significant funds this season to make those changes. He's brought in younger players which I agree with. But I would think that if Arsenal don't get into the top four there will be a review.
"They can't get into the same position as with Arsene Wenger where 50% of the supporters want him to stay and the other 50% want him out and every time something goes wrong on the pitch it's almost as if the supporters are in crisis with each other.
"It wasn't pleasant sitting and watching those games at the very end of Arsene's reign. It was very uncomfortable as a former player to watch on from the sidelines."
Winterburn also flagged a potential replacement for Emery should the Gunners decided to cut ties in the shape of ex-teammate Patrick Vieira who is currently in charge at Nice. Bookmakers have the Frenchman pegged as a 7/2 shot in the next Arsenal manager betting market.
Winterburn continued: "I would say keep an eye on what's happening with Patrick Vieira. If someone like that could prove they are able to run a club in the right way then Arsenal may look towards them eventually.
"Unai Emery could get everything right in the next 3-6 months. If he can get back into the top four and the Champions League, he could very well be with the club for a decent spell longer."