And the England player failed to convert a hat-trick of decent opportunities during Sunday's frustrating goalless draw with struggling West Ham at Villa Park.
But Petrov is adamant the Villa players have faith in Agbonlahor although he admits they have to concentrated more in front of goal.
The Bulgarian international said: "Is Agbonlahor suffering from a lack of confidence? No - and in fact, he is playing very well.
"Please also remember that in footballing terms, he is still a young boy. He is still learning.
"He has already got nine or 10 goals under his belt this season. He is doing really great and everyone has got faith in him.
"It is a fact that sometimes forwards miss chances but we have complete belief in him."
But Petrov also conceded after his side's third successive goal blank in the Premier League: "Probably we need to be more concentrated in front of goal and try to kill off these games.
"Even last season we had games like the one against West Ham when we were dominating the opposition, were on top of them but couldn't score.
"We know we have the boys in the team who can score goals.
"They like to score goals and they get really frustrated when they come off and haven't put the ball in the net."
Villa manager Martin O'Neill is playing down his side's recent league run - one point and no goals from their last three games - ahead of Wednesday's home Carling Cup semi-final, second leg clash with Blackburn.
He said: "I am delighted someone brought up we've gone three league games without a goal. They are a real bundle of joy. Can they narrow it down to the number of minutes we haven't scored?
"Unbelievably, I thought we scored on Thursday in the first leg of the Carling Cup semi-final. We've also taken one point from a possible nine which I'm sure I will be reminded of as well.
"But I think in the two league games we've had at home, against Liverpool and West Ham, we've got one point from those and, if we had four on the board, I don't think the opposition could have complained."
Villa midfielder Nigel Reo-Coker looks set to miss the second leg with an ankle injury suffered in a training ground practice game ahead of the clash with the Hammers.
O'Neill said: "Nigel got injured on Saturday. His ankle has definitely swollen a bit. Wednesday might be too early for him but I am hoping he could be available for Saturday (against Brighton in the FA Cup)."
Hammers boss Gianfranco Zola has faith in his players to climb clear of the relegation zone after holding Villa ahead of crunch clash with fellow strugglers Portsmouth.
He said: "Picking up a point at Villa is not an easy task. That will give the players a big, big boost of confidence and many, many positive things.
"Now we are going to play another tough match against Portsmouth and then we will have a run of good games at home and it is a big opportunity.
"The Villa game is going to prepare ourselves in the best way for the next run of games.
"Is it a chance to move clear of danger? I think so because we have important players coming back and the performance at Villa provided the perfect platform for us for the future.
"I am delighted and lucky to have a bunch of players who are fantastic with their commitment and passion and desire to please me and club and the fans.
"That is a very good thing, the best ingredient to have success, so I'm very confident.
"If we perform like that, and have everyone back, it depends on us but we are good enough to stay up and to be start climbing the league."