Bob Casey and his London Irish players have to overcome the meanest defence in English rugby when they tackle Guinness Premiership leaders Sale at Reading tomorrow night.

To make their task even tougher, Sale are desperate for revenge after the Exiles' surprise 17-7 win at the end of last season ruined their bid for a play-off place.

Irish centre Seilala Mapusua scored a try in that shock away win — the last Sale conceded in the Premiership.

They have gone four games this season without the opposition crossing their line.

Sale's defence, featuring the fearsome tackling of Sebastien Chabal, the bearded Frenchman, has repulsed all comers for an amazing 321 minutes.

The Irish will need all their heavy artillery which makes captain Casey's recent weight loss discomforting news for home fans, although the big lock is hardly fading away.

Casey is almost a stone lighter at 19st thanks to the kind of carbohydrate diet restrictions that would find favour in Hollywood.

While Californians love to live by the "no carbs after 5pm" rule, at Irish the mantra is "no carbs after noon" and that has left Casey with what he describes as "saggy-arsed jeans".

He said: "With the introduction of new rules in England this season we recognised that some of the bigger guys in the squad — like me — would have to make sure they were more mobile and that meant losing weight.

"Now, being a good Irish boy, I love my spuds, but they are off the menu.

"By not eating any carbs after 12noon I have managed to shift nearly a stone and I'm feeling fantastic."

A frustrating period as a spectator after Casey suffered a broken hand ended at Harlequins on Saturday when he came on as a replacement to help Irish produce an amazing second-half revival that saw them win 28-27.

They are now sixth in the league despite having to operate without injured key backs Mike Catt and Shane Geraghty, flankers Keiron Roche and Declan Danaher plus Kiwi prop Clarke Dermody.

Casey's own injury blow came on top of the departure of Brian Smith, the director of rugby, who is now England's attack coach.

He said: "Brian's departure left us in a difficult situation, but the reaction from the staff and the players was great and we have shown tremendous spirit to also deal with those injuries.

"I was thrilled to finally get back onto the pitch and with a bit of luck, we could have been higher up the league table which makes this home game with Sale even more important.

"There is break in the league programme after Wednesday night and we want to end this part of the Premiership campaign with a vital win."

Irish have won their last three matches against Sale and the presence of Casey alongside lock Nick Kennedy, one of Europe's outstanding line-out forwards, will be a major concern to the opposition.

On Saturday, the Quins line-out throw was raided at key points during the second half and Irish are extremely dangerous from turn-over ball.

Irish made the Heineken Cup semi-finals only to fail to qualify this season and that was a hammer blow to everyone at the club.

Casey has only now started to deal with that disappointment and admitted: "I found it really hard when the pools for this season's cup competition were drawn. Not being in it is a bitter blow because I believe this club deserves to be playing at that level.

"We want to win some silverware and besides the Premiership we are also targeting the European Challenge Cup.

"However, first we have to deal with Sale, who won't need any motivation after what we did last season."