The Claret and Blue did manage to win the friendly encounter by the desired two goals to progress to Friday's semi-final but success came at a cost with Petrov being taken off just 21 minutes in.
The Bulgarian's injury drew instant comparisons with Dutch defender Wilfred Bouma's dislocation during the Intertoto Cup last season but thankfully Petrov should not miss out for anywhere near as long as his teammate did.
Bouma was ruled out for the whole of last season after sustaining an horrific ankle injury against Odense but Petrov will be determined to return before the end of September.
The injury was a sour note on what was a very sweet night for all Villans. Marc Albrighton, John Carew and wing wizard Ashley Young all netted to set up a meeting with Porto.
Curtis Davies had put Villa in big trouble as he diverted a cross past Brad Guzan on 20 minutes.
And the emotions of Martin O'Neill became even more frayed as just a minute later Petrov went down under the challenge of an Atlante player and that was the end of his night.
Prosperous
Albrighton, Villa's newest hotshot, then burst into life as he kept calm to level matters after Carew's inital header had been parried by the opposition keeper.
Norwegian striker Carew got on the scoresheet just after the break as he was on hand to side foot home a ball which fell to him virtually on the penalty spot.
Villa knew they just needed one more goal to progress from the group stages and star man Young duly provided with a superb header after yet another brilliant run from Albrighton ended in an inch perfect delivery.
The night may have been marred by the Petrov blow, but O'Neill will certainly be sure that this competition was worth entering.
Albrighton for one will have found the whole experience particularly prosperous and he has most definitely put himself in the first team picture for the season ahead.
Petrov, however, has not been so lucky and he will be worried that the captain's armband, which seemed destined to be his, will now be handed to someone else.