Blackburn - Blackburn Rovers came from behind to beat Arsenal 2-1 at Ewood Park on Monday and leave third place in the English Premiership up for grabs.
David Dunn cancelled out Robin van Persie's opener before Christopher Samba scored the winner to stun the visitors.
A win for Arsenal would have confirmed third place in the Premiership and direct qualification for the Champions League group stage.
But bitter north London rivals Tottenham can now move to two points behind them if they win at Manchester City on Wednesday, meaning Spurs could pinch third place should they win and Arsenal lose in Sunday's final round of matches.
The win saw Blackburn overtake Fulham, Sunderland and Stoke and move into 10th place in the table.
Netherlands striker van Persie put Arsenal ahead in the 13th minute with his first goal since October 31 following his five-month ankle injury lay-off.
Midfielder Dunn levelled in the 44th minute with a tap-in at the far post as the Gunners failed to deal with a Rovers corner.
Congolese centre-back Samba scored the winner with a 68th-minute header.