Falcao struck four second-half goals to help Porto battle back from a half-time deficit against Villarreal and leave the Portuguese giants all but through to the Europa League final.
Villarreal took the lead on the stroke of half-time through Cani but Porto, led by the prolific Falcao, hit back with five goals in a stunning display after the break to take total control of the semi-final.
Falcao won and converted a penalty to draw Porto level and, after Fredy Guarin had made it 2-1 to the hosts, the Colombia international netted further goals in the 67th, 75th and 90th minutes to complete a remarkable comeback from Andre Villas-Boas' in-form side.
Benfica will take a slight advantage into the second leg of their all-Portuguese semi-final following a deserved victory over Braga at the Estadio da Luz.
The hosts dominated for long periods but victory was only secured by a thumping Oscar Cardozo free-kick on the hour mark.
Only nine minutes earlier Benfica had finally been rewarded for a dominant first half when Jardel poked them ahead, but in between Braga claimed a valuable away goal when Vandinho glanced in a Hugo Viana free-kick.
It could prove an important goal from the veteran Brazilian although he will miss the second leg after picking up a first-half booking.
Benfica will also be without their key playmaker Pablo Aimar after he was cautioned for the foul that led to Vandinho's goal.
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