Petrov started treatment for his condition this week in a London hospital and, in his absence, Agbonlahor has been installed as Villa captain. But the England striker will be a happy man if he has to hand the armband back to Petrov as it will mean he has made a full recovery.
"The news about Stan (Petrov) was a massive shock. For someone who's as healthy as Stan, it was very shocking. But he showed bravery to come to the Chelsea game at the weekend," Agbonlahor said.
"He knew he would have been asked a lot of questions and came and showed what a big effect he is to the players and also what a big captain and we're all ready for him to battle through this.
"It's hit the players hard. I think they showed great fight on Saturday for Stiliyan and were unfortunate not to get the right result. I think everyone's close to Stan anyway and everyone's been in contact with him, and he's going to keep in contact with everyone on his progress.
"He's done fantastic for this club, he's been a great example, and everyone is hoping that he can get through this and then come back and captain us all again."
Petrov's enforced absence meant Villa were without eight senior players against the Blues and they will visit Liverpool on Saturday just five points above the relegation zone.
But Agbonlahor said: "We're not looking at it like that. We're just looking at every game, trying to win the games and hopefully can get the results we need. We're going to go there looking for a result. I think they'll be looking to get the fans on their side after some disappointing results for themselves.
"We know it's going to be tough but, as long as we start the game in a good manner, then hopefully it will be a good outcome.
"People mention Liverpool's recent results but, then again, you can say they won the Carling Cup so it's hard to judge them on their season. They've had a lot of new players come in as well."
Source: PA
Source: PA