Sergio Ramos was replaced in the 70th minute of Real Madrid's 3-1 win over Napoli on Wednesday after taking a knock to the right knee.
The substitution is likely just a precautionary measure from Zidane as it appeared the defender was in no serious trouble when he exited the field of play.
Pepe makes comeback
However, the captain did look to be suffering some problems from as early as the first minute of the Champions League 2nd Round 1st leg match at the Bernabéu, raising his hand to the bench after a tackle from Callejon. Ramos also looked to struggle to keep up with Insigne during Napoli's opening goal.
Nevertheless, Ramos continued until he was taken off with just 20 minutes left, replaced by Portuguese centre-back, Pepe, who made his own comeback from injury after a spell on the sidelines.