Two errors from Arsenal 's goalkeeper Lukasz Fabianski allowed Porto to establish a 2-1 lead in the first leg of their European football Champions League last 16 tie in Portugal.
The 24-year-old Pole started in place of the injured Manuel Almunia but gifted the hosts an early lead with a soft own goal before the 35-year-old veteran Sol Campbell equalised.
Then Fabianski inexplicably picked up a back-pass to give Porto a chance to score their second five minutes after halftime.
Ruben Micael took a quick free-kick and Falcao rolled the ball past a stranded Fabianski to secure a slim advantage for his side before the second leg on March 9.
