Real are enduring a dismal campaign with the Champions League now their only hope of securing major silverware.
Zinedine Zidane’s men hold a 3-1 advantage over PSG going into the second leg of their last-16 tie at the Parc des Princes.
PSG will be without Neymar for the encounter because he needs surgery on a metatarsal injury suffered against Marseille last weekend.
The latest reports in Spain suggest Ronaldo has delivered a similarly worrying fitness update on one of his own team-mates though.
In reference to Modric, Diario Gol claim Ronaldo has admitted: “He does not play against PSG.”
And that’s said to have concerned Real skipper Sergio Ramos and Bernabeu president Florentino Perez.
Modric is known for his ability to dictate play at the heart of Zidane’s midfield.
And it seems Isco or Marco Asensio will now have to be entrusted with that role.
Perez has attempted to speed up Modric’s return from the muscular problem by telling Real’s medical staff to focus on him.
However, Modric is not the only injury doubt for Tuesday’s trip to PSG.
Marcelo and Toni Kroos could both miss the clash too.
Theo Hernandez might step in for Marcelo, although reports have indicated Ronaldo would not be in favour of that selection.