Colin Kazim-Richards's 72nd minute goal ensured second-tier Blackburn Rovers dumped a stunned Arsenal out of the FA Cup with a 1-0 win at the Premier League aristocrats' Emirates Stadium on Saturday.
It was the first time Arsenal have exited the competition at the hands of lower league opposition since Arsene Wenger took charge of the club in 1996.
And this defeat came as a major blow ahead of the Champions League visit of Bayern Munich on Tuesday, with Arsenal desperate to end a major trophy drought stretching back to when they last lifted the FA Cup in 2005.
But for Indian-owned Blackburn, a victory that took them into the quarter-finals of the FA Cup marked a rare high-point after an extended period of decline marked by last season's relegation from the Premier League.
Arsenal dominated the game for long periods but Kazim-Richards, a boyhood Arsenal fan, made the most of a rare opportunity midway through the second half.
And the final whistle was greeted with loud boos from home supporters who made it clear they were unhappy with Wenger's team selection.
The significance of the visit of Bayern was reflected in Wenger's decision to make seven changes to the side that won at Sunderland and rest a number of his bigger names, who are certain to start against the Germans.
The manager decided against risking Jack Wilshere's thigh injury and the midfielder was joined on the substitutes' bench by Theo Walcott, Lukas Podolski and Santi Cazorla.
The decision prevented visiting Bayern scouts from getting a good look at the players Wenger expects to influence the Champions League clash -- but there was little else to concern the German club.
As expected, Arsenal -- already knocked out of the League Cup by fourth-tier Bradford this season -- dominated possession against a side still struggling to adjust to life in the Championship.
The pattern of the match would have been very different if Blackburn midfielder Markus Olsson had not volleyed wide from close range after being left unmarked at a third minute free-kick.
From that moment, the visitors were forced onto the back foot and offered little as an attacking force.
They did, however, present formidable resistance and Arsenal's attack, spearheaded by Olivier Giroud, struggled to find a way through a crowded and determined defence.
It was a measure of Rovers' efforts that Jake Kean, the goalkeeper, had a relatively quiet opening 45 minutes although he did produce two excellent saves when called upon.
The first came from Abou Diaby's powerful downward header midway through the half, a minute before the keeper again responded well to claw away Laurent Koscielny's effort.
Both those chances came from corners, but in open play Arsenal found themselves unable to find a way through until Tomas Rosicky picked out Gervinho's run between the Blackburn centre backs.
The Ivory Coast forward impressed during the African Cup of Nations but on his first appearance since returning from South Africa, steered his effort wide.
And there was more frustration to come for Arsenal after the break, when they were arguably even more dominant than in the opening period.
Giroud saw a header saved and Diaby and Rosicky both fired wide before Rosicky sent a powerful shot against the crossbar.
Wenger had seen enough and introduced Walcott and Wilshere from the bench in the 70th minute in a bid to trigger a break in the stalemate.
That promptly happened -- but not in the way Wenger planned.
A minute after the double change, Rovers made a rare breakaway. Martin Olsson fired a powerful left foot shot that Wojciech Szczesny could only parry and Kazim-Richards's mis-hit follow-up bounced into the net.