The stalemate at St Andrew's was North End's fourth draw in the league on the bounce, with it extending their unbeaten run in all competitions to eight games.
It was the opening 20 minutes or so which provided most of the entertainment with chances at both ends.
But in the end the teams cancelled one another out somewhat.
Lilywhites head coach McAvoy said: "I didn't think either of us did enough to win the game if I'm being honest.
"Probably in the first half in chances we had the better ones but over the piece both lacked that bit of quality in the final third.
"We set our intention at the start of the second half, you could we were desperate to try and get the first goal.
"The longer it went on at 0-0 it becomes a mind set, making sure you don't lose the game and are a bit more cautious.
"We tried to win it by putting Josh Murphy up front with a bit more pace but we didn't create enough to go and win the game."
"It was a lively start, Birmingham had a good chance with Troy Deeney's header which flashes by and catches the outside of the post.
"I didn't think they caused us too many problems, they had one in the second half when Bela got in behind Sepp and cuts it back from which Daniel Iversen made a good save for us.
"Other than that I didn't think we were posed many problems and difficult situations.
"Defensively our boys stood up well, it is another clean sheet, if we are not going to win the game, make sure we don't lose it.
"The disappointing thing was that we had a couple of chances which we should have put away.
"There were a couple of things near the edge of the box when we could slide things through, our decision making needed to be a bit better."
McAvoy named Paul Huntington among the substitutes after a knee injury ruled Liam Lindsay out.
Huntington was registered in PNE's senior squad with the EFL which now has its full quota of 25.
Down the line they might be able to take Connor Wickham out of the squad if the diagnosis of his hamstring injury proves serious.
Clubs can apply to the EFL for such a move in the case of a long-term injury.
McAvoy said: "We are hoping Liam is not too bad but I didn't want to leave ourselves short at the back with centre-backs so Hunts has come in.
"We will see how Connor is once we get the specialist's opinion and recommendations, We'll see what happens."
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