Simunovic joined the Bhoys over the summer from Dinamo Zagreb, as Ronny Deila looked to fill the void left by Virgil van Dijk and Jason Denayer’s departures.
The Croatian has not played too frequently so far, but Petrov has been impressed by the fleeting glimpses he has caught of the young defender.
“He’s very calm. He’s better on the ball than all the defenders at Celtic at the moment,” Petrov said.
“I think that when he plays, he gives Celtic some insurance at the back. He can organise defences and take that responsibility.”
Simunovic’s performances have been impressive when he has been on the pitch, but his injury problems have been a worry so far.
The 21-year-old has endured a series of knocks, and every time he appears to be making a comeback, he seems to have suffered a fresh setback.
Simunovic started Celtic’s match against Molde in the Europa Leagueon Thursday night, but he had to go off after five minutes, and that change seemed to disrupt the side.
The Bhoys never got going against Molde and fell to a 2-1 defeat, leaving their chances of qualifying from their Europa League group looking very slim.