Webb was named in Rhinos' initial 19-man squad yesterday, but a club statement today revealed he will not play at Old Trafford due to a recurrence of a back problem, which saw him miss three games in July - including the Carnegie Challenge Cup semi-final defeat by St Helens.

Webb suffered a knee injury in the qualifying semi-final at Saints two weeks ago, but played in last Friday's final eliminator against Wigan Warriors.

The Kiwi Test ace - who will not be fit enough to travel to Mancester to watch tomorrow's game - could also miss the World Cup, which kicks off in Australia later this month.

In a statement issued by the club, Rhinos coach Brian McClennan said: "We are all behind Brent at this time and he is bitterly disappointed to be missing out. We were confident earlier in the week that he would be available, but then he suffered a re-occurrence of the back injury in training.

"The last time he suffered it he was out for three to four weeks and it is worse this time. He has been a huge contributor to our team and to getting us to the Grand Final.

"It is probably the worst week in his sporting life, he is devastated to miss out on Old Trafford, having missed the semi final earlier in the year, and also possibly representing the Kiwis in the World Cup.

"He has wished the boys all the best and he will have to watch the game at home because he is in so much pain that he can not even sit down in comfort. Our medical staff are working with him to help him as much as they can and he knows he has got our full support."

Rhinos have decided against drafting anybody else into their squad for romorrow, so Lee Smith is likely to switch to full-back, with Ryan Hall - who has not played since suffering a broken foot in the Challenge Cup clash with Saints on July 26 - coming in on the wing.