City are nine points behind Premier League leaders Liverpool.
McAteer told the Racing Post: "City are a side who tend to bounce back from setbacks by going on unbelievable winning runs.
"They have issues at the back which need addressing and they need to get to the start of the January transfer window without losing any ground. Perhaps Pep will then go in for another centre back.
"It looks as though he might have no choice with Aymeric Laporte sidelined until at least February and Fernandinho being found out. I'm just not sure Nicolas Otamendi and John Stones are good enough."