While every player gives his best in a big game like the Champions League semi-final, a few will be thinking twice this week before making that desperate lunge in defence or arguing with a referee's decision.

Manchester United have Cristiano Ronaldo, Patrice Evra, Gabriel Heinze and Paul Scholes all one card away from suspension, while Milan have just Paolo Maldini risking an enforced seat in the stadium for the return leg. While losing Ronaldo would be devastating to United, I believe Evra and Heinze pose a greater problem for them.

If either or both are suspended for the second leg, it would put tremendous pressure on United's playing strength. It would probably force them to bring back at least one of their injured stars and  risk not having them for the final stretch of the Premier League should they sustain further injury. While losing Maldini would be a blow for Milan, Kakha Kaladze and Daniele Bonera wait in the wings, capable of stepping in.

'Drogba may prove slightly less of a problem for Liverpool if he backs off a bit to ensure he isn't booked'

Liverpool only have Jermain Pennant at risk, which I doubt will have Rafa Benitez overly worried, although his absence in the second leg would restrict Liverpool's options if they were trying to chase a Chelsea lead. Chelsea have Michael Ballack, Joe Cole, Lassana Diarra, Didier Drogba and Arjen Robben at risk. Drogba would probably be the biggest loss and he may prove slightly less of a problem for Liverpool if he backs off a bit to ensure he isn't booked. Cole, Robben and Ballack would also be losses although Robben is unlikely to take part in either leg due to injury.

It will be interesting to see how each player performs under such prospects and whether or not their coaches try to protect them. It's just another dimension of what should be two fantastic semi-finals.

In such important games, will players on a yellow card really back out of crucial challenges for fear of missing the return leg? Send your views to Sportingo.