As many as 12 Nottingham Forest and Porto are at risk of missing the second leg of their Europa League quarter-final.
Premier League club Forest are currently preparing to make the trip to Portugal to face the top-flight leaders at Estadio do Dragao.
Vitor Pereira is also making a return to one of his many former clubs, with two Primeira Liga titles being lifted during his time at Porto.
Forest have not played a competitive fixture since they beat Tottenham Hotspur before the March international break, while Porto returned to action on Saturday as they were held to a surprise 2-2 draw by Famalicao.
Although both clubs have ambitions to win this competition, there is the potential for a number of absentees for the second leg at the City Ground next week.
Which Nottingham Forest players are at risk of Europa League ban?
Key midfielder Elliot Anderson is already missing for Forest as he serves his second Europa League suspension of the season.
However, more important squad members will miss the reverse fixture if they receive a yellow card on Thursday night.
Murillo, Morgan Gibbs-White and Igor Jesus all fall into that category and will be eager to avoid any issues.
Morato and Ryan Yates are also one caution away from being unavailable for the fixture in the East Midlands.
Which Porto players are at risk of Europa League suspension?
Meanwhile, Porto incredibly have seven players who are bidding to avoid a booking on familiar territory.
Jan Bednarek and Pablo Rosario, who have already made nine starts in this year's competition, are two notable squad members at risk.
Playmakers William Gomes and Rodrigo Mora - who have three goals apiece in this competition - fall into the same category.
Alberto Costa, Dominik Prpic and Zaidu Sanusi are the other three players who have already received two yellow cards in this season's tournament.