Los Blancos travel to the Etihad Stadium on Tuesday night for the first leg of a tie that may prove to be the toughest game of the season for both sides. One of the competition's biggest teams will crash out in the play-offs and McManaman spoke to Mail Sport about how Mbappe must put in a performance of a lifetime to help his team progress.
"Everything is on the line for both (teams), and individually, everything's on the line for the players as well.
"If you want personal titles, if you're Kylian Mbappe and you want to be a Ballon d'Or winner in your first year at Madrid, they're going to need to win (the Champions League).
"Likewise, for individual awards for the Manchester City players, Erling Haaland hasn't scored against them. He's going to be up against the inexperienced defenders this time around, so he has to make a big play for himself as well. So, there are loads of little conundrums."
The reigning Premier League champions will be hoping to make up for their disappointing campaign by winning a second Champions League crown under manager Pep Guardiola and believes they have no excuses coming up against an injury-laden Madrid side.
"They are meeting a Real Madrid absolutely decimated defensively. Dani Carvajal is out, (David) Alaba's out, (Antonio) Rudiger is out, Eder Militao is out.
"City can't complain necessarily about their injury problems when you can reel off a list of defenders missing the game like that."