Chelsea had just crashed to their second successive Premier League defeat, and had found themselves 3-0 down after just 40 minutes at the Emirates, as Arsenal looked rampant.
Conte, recruited in the summer after leaving the Italian national team job having reached the quarter finals at Euro2016, was facing the first real test of his credentials.
What happened next is now history. Conte decisively changed Chelsea’s system – he actually did it at half time at the Emirates as he moved from 4-2-3-1 to 3-4-3 – and now, his team are Premier League champions.
Arsenal, who effectively saw Chelsea disappear over the horizon after that day last September, are the opponents today in an FA Cup final that could see Conte emulate Carlo Ancelotti in winning the Double in his first season at Stamford Bridge.
Antonio Conte admits he was very angry following the defeat to Arsenal earlier in the season
But that afternoon in North London, that prospect seemed very far away indeed.
“After that Arsenal defeat, I was angry,” said Conte. “It was difficult for me to accept. For two days, it was not easy for my family to live with me, but they understand. But I channelled my anger in the right way. I tried to change the situation.”
Though he never put pressure on his manager, owner Roman Abramovich was demanding answers.
“Honestly, I was very calm,” said Conte. “I knew that I was putting all of myself, all my strength, into this new job.
Arsenal v Chelsea combined XI Fri, May 26, 2017
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I was lucky to have a group who put themselves into my idea of football
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“Myself and my staff were working so hard.
“To find the right solution quickly is not easy. You must be very good, very prepared, but also lucky . You must have the players to give you the possibility to impose your ideas.
"I was lucky to have a group who put themselves into my idea of football, and we put ourselves in a position where we could secure a fantastic title.
“The owner came for three days to watch our sessions, watch the video analysis, to stay with us. He supported me. He never showed me he was angry.
Antonio Conte changed Chelsea's formation after the loss to Arsenal
"The club always trusted me. I never thought the club was thinking about sacking me.”
Chelsea can win their eighth FA Cup this afternoon, and their fifth in the Abramovich era.
The Italian did not go wild celebrating the title win but he might puff a celebratory cigar if his team lift the Cup today.
“We have to make it a fantastic season. There’s only one way to do that, by winning,” he said. “I don’t smoke, but I’m ready to smoke a cigar if we win,” he said.