A replay a week on Wednesday will pay off another chunk of their £30million debts and, judging by their performance in this game, Villa's favourites tag will not overaw them.
After all, the Eagles had looked to be heading through to the last eight at the first attempt when Darren Ambrose made it 2-1 with a superb 35-yard free-kick, but Petrov headed a second equaliser three minutes from time to save Villa's blushes.
It was harsh on the hosts, who looked good value for their lead and had restricicted their Premier League opposition to next to no attacks in the second half.
But Petrov's goal three minutes from time leaves Palace hoping they can cash in on another televised encounter to bring in another £250,000 and further ease their financial woes.
To say Palace were up against in this tie was an understatement.
The club went into administration a fortnight ago with those staggering debts. The players' futures are uncertain, manager Neil Warnock does not know if he will be in a job from one week to the next and the canteen lady has not been paid for two months.
There have been lots of beans and toast on the menu at the club's Beckenham training ground but you cannot fault the spirit in the side.
And for long periods in an entertaining, at times pulsating cup tie, they gave as good as they got. As good as Warnock had promised, in fact, when he predicted they would not go down without the mother of all scraps.
Ambrose up front was a constant threat. Neil Danns was also a menace and if Danny Butterfield could not conjure up the six-minute hat-trick which dispatched Wolves in the last round then he epitomised the buckets of sweat shed by the south London team.
But give Villa credit. Martin O'Neill paid Palace the respect of fielding his strongest side with Emile Heskey up front and Stewart Downing and James Milner in midfield.
But it was Palace who took the lead after 24 minutes from an unlikely source.
Austrian defender Johnny Ertl had never scored for Palace in two years at the club. But he might well never have had a better delivery come his way, a corner swung in by Ambrose which homed in on Ertl's bald pate.
A quick flick of the neck and the ball flew past goalkeeper Friedel and the cup upset appeared to be on, even if the goal did come against the run of play.
If Danns' crisp shot had also found its way past Friedel then Villa would have been in trouble.
As it was Villa composed themselves and announced their intention to scrap just as hard as their Championship rivals.
When the equaliser came it had the mark of England quality. It was also a carbon-copy of the Palace goal.
This time it was Downing who threw in an inswinging delivery from the right and Villa defender James Collins rose above everyone to head home from inside the six-yard box.
It was no more than Villa deserved, although the last action of the first half saw Friedel scrambling away a 25-yard thunderbolt of a free-kick from Ambrose.
Villa should have taken note, especially when Ambrose lined up another in he 69th minute.
This one was further out, some 30 yards or more, but the strike was even better this time, arrow straight and it was past the despairing dive of Friedel in the blink of an eye.
What a wonderful strike. What a way to win a football match. Except it did not. Because Petrov swooped to get Villa out of jail. They barely deserved it.