Arsene Wenger has won the FA Cup more often than any other manager in the competition’s history but there was something he had never experienced.
Until Sunday, that is, when he suffered his first third-round defeat in his 21-year reign.
It amounted to another of the ignominious days that have pockmarked the latter years of the Frenchman’s reign, but a glorious occasion for Nottingham Forest, deserving winners who played with a vibrancy, an energy and a coherence that a shambolic Arsenal side lacked.
Forest, five games without a win and without even a manager – Gary Brazil is only a caretaker after Mark Warburton’s sacking – appeared unlikely candidates to spring a shock.
Every now and again, however, the improbable happens in the FA Cup. And so it was that right-back Eric Lichaj, whose first 181 games for Forest had produced just four goals, was on a hat-trick before half-time.
The American’s opener was a header from a yard but his second goal was a beauty, a volley into the top corner after he cushioned the ball on his chest, that felt equally out of character.
He was far from Forest’s only hero. When Ben Brereton calmly converted a penalty, awarded after Rob Holding tripped Matty Cash, it brought him the goal he merited.
Forest looked to get the striker running at, or behind, Per Mertesacker and the 18-year-old ran the Arsenal captain ragged. He set the tone for his team.
Mertesacker, who has played in three FA Cup final wins in the last four seasons, scored Arsenal’s first goal but still had a torrid time on what will be his last appearance in the competition.
Forest scored a second penalty, with Arsenal claiming Kieran Dowell touched the ball twice as he slipped, but the end result was that they conceded four goals in an FA Cup game for the first time in a decade.
This could have been more gruesome for Arsenal. It was damning that their best player was their goalkeeper. David Ospina, deputising for the rested Petr Cech, made a terrific save from Cash and two excellent stops to deny Brereton, who was just too sharp for Mertesacker to handle.
Wenger was confined to the stands, serving the first game of his touchline ban and presumably ruing his side’s wretchedness.
His decisions contributed. Arsenal were without 13 players, some injured, but Alexis Sanchez, Alexandre Lacazette and Mesut Ozil among those who were simply rested.
There was no cavalry to call upon from the bench, though Eddie Nkietah was lively in his cameo.
Danny Welbeck offered brief hope of a comeback by scoring their second goal and Forest’s Joe Worrall was sent off, but Arsenal deserved what they got: an early exit from a competition they often win.