The 22-year-old picked up the blow during his sides 47-20 victory over Castres in the Top 16 at the weekend and was stretchered off after 34 minutes of play.

Frederic should undertake further medical examinations but we are worried about his participation in the final, said club doctor Christophe Foucaud.

For now Michalak is not capable of playing and a decision will be made after the examinations, which will be carried out at the start of the week.

The absence of Michalak would be a big blow for Toulouse, who outclassed Leicester in the semi-final last month mainly thanks to his leadership and composure.

Captain Fabien Pelous may have returned to competition against Castres on Saturday after shaking off his knee injury earlier than planned, but Michalaks injury adds to those of centre Benoit Baby (thigh), Omar Hasan (left knee) and Gregory Lamboley (left leg), who will definitely miss out.

Toulouse won the European Cup in 1996 and 2003, beating Cardiff Blues and Perpignan respectively, before reaching the final again last year only to lose to Wasps.

With such European pedigree, they will start as favourites on Sunday, although their France centre Yannick Jauzion believes tactics will have a major part to play.

The match will be won thanks to mental strength and intelligence of the game, he said. The tactical aspect of the game will be essential.

We know Stade Francais by heart, they take risks and have their feet on the ground.

They never give up and their strong mentality allows them to fight back, theyve proved it against Biarritz (in the semi-final).

Stade Francais coach Fabien Galthie has less injury woes to contend with and even rested most of his key players at the weekend, such as Sylvain Marconnet, Pieter de Villiers, Christophe Dominici and Brian Liebenberg.

This did not prevent them from winning 29-24 against Narbonne, though, which took them to the Top 16 leadership.

I did what we used to do with the French national team, explained the former France captain.

We tried to respect the players while sustaining competition between them.

Now we are entering the proper preparation phase for the final, he added.