The Gunners were labelled a "pub team" as they fired blanks and crashed out of the FA Cup at Championship Nottingham Forest to Lewis Grabban's dramatic late winner.
The record 14-time winners of the competition saw their hopes of another Champagne Wembley triumph fall horribly flat here.
They were awful at the City Ground on Sunday where they failed to have a shot on target as boss Mikel Arteta was left fuming on the sideline.
The Spaniard even hauled off left-back Nuno Tavares, making his ninth start for the club, in the 35th minute in an embarrassing substitution.
Portuguese youngster Tavares threw away gloves and ignored Arteta after being replaced by Kieran Tierney.
Did Mikel Arteta make a mistake with his Arsenal line up choice? Have your say in the comments below.
But not even that drastic action was enough to sting Arsenal into life as Forest triumphed to set up an East Midlands derby at home to Leicester in the fourth round.
Unimpressed former Forest midfielder Roy Keane, a pundit at the game, said Arsenal looked like Real Madrid because they wore a one-off white strip as part of the 'no more red' campaign but played like a pub team.
It meant Arsenal crashed at the City Ground again after also losing here as holders in 2018 at the City Ground.
Arteta's decision to make seven changes backfired badly with much-hyped teenager Charlie Patino, 18, underwhelming on his full debut.
While Eddie Nketiah led the line upfront and fluffed some of the visitors' rare openings.
It proved costly for the visitors were also without Granit Xhaka and Folarin Balogun after testing positive for Covid, while Emile Smith Rowe and Takehiro Tomiyasu were absent injured.
Forest appeared fired up from the start as they gave debuts to new signings Keinan Davis and Steve Cook and had Canada international Richie Laryea from MLS side Toronto FC in the stands watching.
The hosts pressurised the visitors from early on as Tavares' awful backpass to Leno forced a corner.
Tavares, 21, signed from Benfica last summer for £8million, struggled to contain the quick duo of Djed Spence and Brennan Johnson early in the first half.
Arteta took no chances and made the brutal decision to sub Tavares before the break which clearly upset the youngster.
The change helped Arsenal improve marginally but it was Forest who almost took the lead after the break.
Johnson did excellently to get away down the right and cut the ball back for Philip Zinckernagel whose first time volley was pushed behind by Leno.
Nketiah, who is out of contract in the summer, blew a good chance from Bukayo Saka's cross to the back post.
Leno at least continued to be steady in goal as he kept out a free-kick from James Garner.
But he was helpless as Grabban poked in an 83rd minute winner for his 11th of the season from Ryan Yates' cross from the right which sparked a mini pitch invasion.