The France international entered Tuesday's contest at Bernabeu knowing that a booking would see him ruled out of the second leg of the last-eight affair in Manchester.
Tchouameni, who was featuring in central defence, picked up a yellow card inside the first minute for a late challenge on Jack Grealish, and Man City took the lead from the resulting free kick.
The 24-year-old's booking was his third in the Champions League this season, meaning that he will be suspended for the return match in England on April 17.
Tchouameni is primarily a defensive midfielder, but he has operated as a centre-back on multiple occasions this season due to the team's injury problems in that area of the field.
Militao or Nacho will replace Tchouameni in the second legEder Militao is now back from a long-term knee injury, but he is still not ready to start, while David Alaba is out until next season due to a serious knee problem of his own.
Either Militao or Nacho will now come into the team alongside Antonio Rudiger for the second leg of the Champions League quarter-final away to the reigning European champions.
«Nacho or Militao will play. The idea for the return has to be this. Don't do a lot of calculations, like last year, and play face to face, like today,» Real Madrid boss Carlo Ancelotti told reporters when questioned on Tchouameni's absence for the return fixture.
«We have confidence that something good can happen. The grass in Manchester is long, like here. We have a small disadvantage there, but the confidence remains the same.»
Tchouameni has again been an important
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