The right-back stepped in goal for the Sky Blues after Ederson's injury and Claudio Bravo's rash challenge on Josip Ilicic that earned him a red card.
With Ederson hooked after the break, Walker took responsibility by going in goal for City, who were drawing 1-1 with the Italian outfit.
Ahead of his side’s Premier League clash with Chelsea at the weekend, the England international remembered the occasion, as City drew on their way to the knock-out stages of the competition.
Speaking exclusively to BT Sport, Walker was reminiscing on that special moment.
"I’m always giving the goalkeepers stick out there, telling them to catch it when they parry it," the right-back said.
"So it was a toss up between me and John [Stones] on the bench, who was going to come on?"
"Who’s the dumbest out of John and Kyle, alright we’re going to pick Kyle today. I think I just got the nod. Luckily enough I did okay, I wasn’t happy with my save, I should’ve caught it."
Maybe the most Typical City moment ever, but it's certainly one Manchester City fans will not forget. And neither will Kyle Walker, whose 100% clean sheet record is still in tact.
"But listen, I kept the ball out of the net and I’ve been in teams where players have fumbled them into the back of the net. I’m more sympathetic to the keepers now, it’s a lonely place back there!," Walker concluded.
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