Real Madrid usually announce their starting lineup two hours prior to every game, which is earlier than any other team in Europe.
"I give the lineup two hours before the match. After the technical meeting, as always. Nothing has changed," Carlo Ancelotti answered when asked why Real Madrid lineups are released earlier than others.
There have been rumors that Real Madrid has a mole in the locker room who leaks the starting lineups to the media, causing the lineup to be revealed early.
Ancelotti, however, is a manager who does not frequently alter his starting lineup unless it is absolutely necessary. Almost nothing needs to be kept secret.