Bulgarian midfielder Petrov, 29, has started the season brightly in the new holding role he will occupy against Litex Lovech in Thursday's UEFA Cup tie.
The last time he faced Litex as a CSKA Sofia player 10 years ago, he was on the receiving end of an 8-0 defeat.
That shocking setback was played out against a backdrop of heavy snow, and adverse weather has returned to the Gradski Stadion; Villa were met by a huge thunderstorm upon arrival here last night and the deluge since prevented them training on the pitch today.
But, having struggled to adapt to the Barclays Premier League since switching from Celtic two years ago, not much can dampen Petrov's current mood, after his career in England was kickstarted by his 50-yard strike against Derby in April.
"He's had a great start," said O'Neill, who has tapped into Petrov's knowledge on the opposition.
"At the back end of last season he got a bit of confidence, he moved into what you would perceive as the kind of holding midfield player and almost swapped positions with Nigel Reo-Coker, who advanced more.
"Although that was not Stiliyan's position when he played at Celtic, he has adjusted very well indeed.
"He is capable of doing it because he has got a bit of discipline about his game but more importantly he has got confidence from it.
"That confidence has come from a couple of good performances at the back end of last year, you never know, it might sound a bit strange, I haven't really talked to him about this, but maybe even the great goal he scored against Derby gave him a boost because that is something he had stopped doing.
"While his input at this minute in terms of goals has not been great, his overall contribution to the side has been terrific this season."
Petrov's high-energy displays have also been a feature for the Bulgaria national team, which he temporarily quit in the winter of the 2006-07 season because of his acrimonious relationship with then coach Hristo Stoichkov.
Intriguingly, he later returned to play under current Litex boss Stanimir Stoilov last year, who took the Bulgaria job on a caretaker basis before moving to the country's reigning cup holders.
Litex finished fourth last season, are currently second in the Bulgarian top flight and will prove tricky opponents on a saturated surface.
Slight doubts over the playing of the fixture emerged due to the heavy rainfall today, but O'Neill declared: "The pitch is in good shape.
"It's a really good pitch but there have been puddles on it and they were concerned about forking it today.
"We could have insisted on training on it but we haven't done, the players have just come for a look at it first of all - I don't see it being a major problem.
"The weather forecast for tomorrow is a bit brighter and it should be fine. They can fork the pitch in the morning and get the excess water off."
A postponement would not be welcome for Villa, whose first European campaign for seven years means a bigger fixture list.
And O'Neill is prepared for a challenge comparable to the one Villa narrowly overcame against Danish side Odense in the Intertoto Cup.
"We have seen videos of them and the players will have looked at those before the game," O'Neill confirmed.
"But we have sent someone out to the games here, who was the same man we sent out for the game in Odense.
"He said we would definitely have problems against the Danish side and that is how it turned out to be.
"He didn't feel the Icelandic team would be as strong and that is how it turned out to be, and he said this is a very, very decent footballing team.
"We cannot treat it lightly. We are not capable of playing in second gear and winning games like that at the moment."
There are likely to be changes to the visiting XI with John Carew (ankle) back home recuperating and Ashley Young nursing a knee injury, which has made him a doubt.
James Milner, the US$21.47million (£12m) capture from Newcastle, is a certain starter, Marlon Harewood comes into the equation and there will need to be a change of tactics due to the loss of powerhouse Carew.
"With the loss of John Carew we might have to adjust and adapt, and it might be pretty good to do a bit of that, with players maybe playing in different players overall," said O'Neill, who could also hand a debut to Spanish centre-back Carlos Cuellar.
"The idea of trying to get a few players in this season was to cope with the things that we had."
Their strength in depth will therefore be tested for the first time, and Stoilov was in awe of Villa's first-choice XI earlier this week.
"I am very afraid of Aston Villa because they're a very strong team," he said. "I watched the game against Tottenham on Monday and I am very scared. They were perfect against Tottenham. But we will be looking for the win from the first minute."