Warnock was back in action for Villa's FA Cup draw against Crystal Palace.
"He's been out of the side for a few weeks and hasn't trained properly, yet he's performed brilliantly after that time on the sidelines," said Petrov. "He's played and he hasn't felt anything [in the shin], which is really promising. He's looking after himself, he's a fit boy and, when you've got players like that, the manager really trusts them.
"It's great to have him back because he gives us a different dimension at left-back. We haven't had that for a long time since [Wilfred] Bouma got injured. Stephen came into the side and had been playing brilliantly. Why wouldn't he be in contention to go to South Africa with England? He's been playing magnificently and has got every chance of making Fabio Capello's squad for the World Cup."