SARACENS' chief executive Francois Pienaar believes Worcester Rugby Club will prove to be a tough nut to crack in the Tetley Bitter Cup fifth round tie on Sunday.

The former South African skipper, who lifted the World Cup back in 1995, knows the Premiership leaders will face a test of character as Adrian Skeggs' men visit Vicarage Road.

He said: "Worcester are unbeaten this season and have their hearts set on a Premiership place next season.

"They will be looking to prove this point by recording a famous victory against us on Sunday on our home ground."

Pienaar received a blow this week when full-back Thomas Castaignede was ruled out after he tore his Achilles tendon.

And he is well aware Saracens' loss will be Worcester's gain at the weekend.

"Worcester offer a real threat and it will be a tricky game. Nothing short of 100 per cent commitment will see us progress to the quarter-finals."

Pienaar added: "We are hampered by international training camps.

"Paul Wallace has left for Ireland for two weeks and Scott Murray is a week into his three-week stint with Scotland.

"The England boys are off for the next few days and with Castaignede ruled out it means we are missing 10 players at present which is hardly ideal."