O’Neill will definitely be without the services of Carlos Cuellar who is suspended following his controversial sending off in Saturday’s 1-1 draw with Everton.
Petrov limped off the pitch following a two-footed lunge by Diniyar Bilyaletdinov which resulted in the Russian being shown a straight red card.
Meanwhile, Milner sustained a calf problem at Goodison Park and was withdrawn at half-time.
“James was struggling a little bit. He had a calf injury and he continued on manfully until we took him off at half-time,” said O’Neill.“Stiliyan’s not so clever at the moment, he obviously tried to play on and we’ll see how he is.
“Their crowd seemed to get upset about it, but I think if they go back they’ll see it was straightforward. Their player’s caught him on the shin.”
Meanwhile, O’Neill was frustrated with referee Lee Probert’s decision to send Cuellar off in the closing stages of the game, adding:“I thought at the time that Carlos got a touch on the ball.
“I’ve seen it back since and it’s pretty evident that that’s the case. I preface everything by saying how difficult the game is now to referee.
“Everybody’s got the benefit of hindsight afterwards, but on that particular occasion I thought it looked relatively straightforward and coming so quickly after the other incident I can’t say that I was overly impressed.”