Brent Webb will miss tomorrow’s Super League Grand Final at Old Trafford due to a back injury.nnThe full-back has suffered a re-occurance of the back injury that kept him out of three games earlier in the season. nnThe New Zealand international picked up a knee injury against St Helens a fortnight ago but that injury had cleared up and the club were confident he would be available.nnLeeds say there is a strong chance that he could even be forced to withdraw from the Kiwis’ World Cup squad, which is announced on Tuesday, although he will have further medical tests next week before a final decision is made.nnWebb will not be able to even travel across to Manchester to watch tomorrow’s game, due to the extent of his injury.nnLeeds coach Brian McClennan said: “We are all behind Brent at this time and he is bitterly disappointed to be missing out.nn”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.nn”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.nn”It is probably the worst week in his sporting life. He is devastated to miss out on Old Trafford, and also possibly representing the Kiwis in the World Cup.nn”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.”nnMcClennan has no plans to add to his original 19-man squad, which means that Lee Smith is likely to switch to full-back with Ryan Hall coming into the side on the left wing.nnThe 22-year-old Smith was also a doubt for tomorrow’s game after being placed on report for kicking out in the tackle against Wigan.nnHe was found guilty of the offence when he appeared before the League’s disciplinary panel on Tuesday, but escaped with a fine.nn”It was a concern,” he admitted. “To miss a Grand Final would have been massive. I felt I got a fair hearing though. It wasn’t intentional and they could see that.”nnSmith, who was a tryscorer from the wing in last year’s Grand Final, deputised for Webb at full-back in the Rhinos’ League win over Catalans in Perpignan as well as the Cup semi-final against Saints.