Erling Haaland and Neymar head the list of high-profile players who could miss their side's Champions League semi-final first leg should they progress this week.
UEFA rules dictate that from the first match in the group stage, players and team officials are suspended for the next competition match after three cautions.
Norwegian striker Haaland was booked in both legs of Borussia Dortmund's last-16 tie against Sevilla, including one caution for unsportsmanlike behaviour after celebrating in goalkeeper Bono's face.
Brazil star Neymar is also at risk of suspension after being cautioned twice in the group stages for Paris Saint-Germain in home games against Manchester United and RB Leipzig.