UEFA has opened disciplinary proceedings against Real Madrid's Dani Carvajal over his yellow card for timewasting against Apoel Nicosia, meaning he could be banned for the round-of-16 first leg in February.
Carvajal was booked by referee Artur Dias for taking too long over a 90th-minute throw in the 6-0 win, bringing an automatic one-match ban that could be served in a group game at home to Borussia Dortmund on Dec. 6.
That would mean the Spain international right-back being free of suspension when the knockout phase starts.
Madrid have run into trouble over alleged deliberate yellow cards in the past, with Sergio Ramos, Xabi Alonso and coach Jose Mourinho punished in the 2010-11 group stages.
All three escaped any further sanction after another incident late in the quarterfinal first leg win over Galatasaray in 2012-13.
Also on Tuesday, Manchester City's Kevin De Bruyne was booked late in the 1-0 Group F win over Feyenoord, meaning he misses the final fixture at Shakhtar Donetsk with a top seeding already secured.