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 match in the competition 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.
They could now miss the first leg of the last four if they are booked in their quarter-final second legs against Manchester City and Bayern Munich respectively.
Bundesliga outfit Dortmund trail Pep Guardiola's men 2-1 after Phil Foden's last-minute strike, but PSG head into their home return leg having claimed a 3-2 win at Bayern thanks to a double from Kylian Mbappe.
Yellow cards then expire on completion of the quarter-finals, and are therefore not carried forward to the semi-finals, which begin on 27 and 28 April.
Haaland's club team-mate Emre Can is the only fellow Dortumd player who risks suspension, but three of Neymar's fellow PSG stars - namely Idrissa Gueye, Layvin Kurzawa and Marco Verratti - risk missing out.
Liverpool meanwhile have five players who could miss their next European encounter through suspension, the most of any side left in the competition.
Trent Alexander-Arnold, Sadio Mane, James Milner and Georginio Wijnaldum will all miss out if they are booked in their bid to overturn a 3-1 deficit against Real Madrid, while injured captain Jordan Henderson is also listed.
Madrid themselves will be hoping left-back Ferland Mendy and Federico Valverde are not shown a yellow card at Anfield too.
Premier League rivals Chelsea and Man City have two players who could be ruled out, with Blues duo Hakim Ziyech and Mateo Kovacic and City pair Fernandinho and Joao Cancelo one booking away from suspension.
Thomas Tuchel's men are favourites to head through having secured a 2-0 victory last week in Porto, who only have former Newcastle midfielder Chancel Mbema at risk.
Bayern Munich trio Jerome Boateng, Lucas Hernandez and star man Joshua Kimmich could also miss the first leg of the last four if they are booked against PSG.
The second legs of the semi-final take place on 4 and 5 May, before the final takes place in Istanbul on Saturday 29 May.