United have lost back-to-back home games in the Premier League.
McManaman told the Manchester Evening News: "United's form has surprised me slightly. I don't expect them to win the league this season. When people asked me at the start of the season what I expected from them this year, I said they would finish in the top four but wouldn't win the title. That opinion hasn't changed.
"You expect United to win at home. That hasn't been happening so that has surprised me.
"They missed a trick by not doing much in the transfer market in the summer. I expect them to buy in January and qualify for the Champions League. I think they will get a lot stronger."
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