The German defender run his contract down at Stamford Bridge to link up with Los Blancos on a free transfer last summer.
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He has become a key player for the Spanish side where he has formed a formidable centre-back partnership with Eder Militao.
And he will now be returning to west London where he is hoping to dump his former employers out of the quarter-finals.
It is third successive season that the two clubs will have played each other in the European Cup.
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Rudiger has revealed he cannot wait to face his ex-Chelsea pals as he took to social media after the draw was made.
He tweeted: "This will be very special - Can't wait to see so many friends again."
Chelsea will also be up against former stars Eden Hazard and Thibaut Courtois once again, while Mateo Kovacic will battle against his old team.
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Despite Real going into the tie as favourites, Chelsea boast a brilliant record against the LaLiga giants.
From their seven matches in European competition, the west Londoners have lost just one match.
And Roma boss Jose Mourinho, who managed both clubs, has stated that he hopes Real Madrid go on and win a record-extending 15th European title.
Speaking before the draw was made, Mourinho talked up his relationship with Los Blancos boss Carlo Ancelotti, who also spent time in Chelsea's dugout.
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He said: "There is a club that is close to my heart and there is a manager who is my friend.
"Real Madrid are great and Carlo Ancelotti is great!
"Hopefully they will go on in this way to win the final."
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