Soccer: Roy Keane has launched a broadside at Manchester United's younger generation and warned them never to forget how lucky they are to play for the club.

The combative Irishman was a frustrated spectator on Wednesday as United slumped to the 3-2 home defeat against Middlesbrough that leaves them five points adrift of Arsenal in the title race.

Like manager Alex Ferguson, Keane is extremely concerned about his team's defending, blaming the current problems on the side as a whole rather than just the back four.

The United captain believes a lack of concentration is a major factor behind the malaise that has seen eight goals conceded in their last three Premiership outings.

However, he is equally fearful that some of the younger players are falling short of the blinkered ambition shared by the elder members of a squad that is widely accepted as the most focused and driven in the Premier League.

"We have worked extremely hard to get to the top but it is a lot harder to stay there," said the 32-year-old. "We have one or two young players who have done very little in the game. They need to remember that and not slacken off. They need to remember just how lucky we all are to play for Manchester United and show that out on the pitch."

Keane will be back at the heart of the United midfield tomorrow when they entertain neighbours City in an eagerly-awaited FA Cup fifth-round encounter.

On paper, it looks like a banker home win but the Cork-born star, who skippered United to their record 10th success in the competition five years ago, knows on current form nothing can be taken for granted.

"I have been critical of our defence recently but it is down to the whole team, not one section of it," he said. "A lot of the goals we have been conceding are from set-pieces when we are all back anyway.

"It is stating the obvious to say Rio Ferdinand is missing but having to cope without certain players is part of football," he added. "You can make all the excuses you want but the players representing Manchester United on Wednesday night were good enough to win. But you can't be going 2-0 down like we did the other night.

"It boils down to a lot of things. We need to be focused and fully concentrated from the start and that comes from training.

"You can't slacken off in training and expect to switch it back on a Saturday. You have to prepare properly and stay focused on what your job is. When you are playing for Manchester United nothing should get in the way."

City arrive at Old Trafford on the back of a 14-match run without a Premiership win. It is almost 30 years since they last recorded a victory at the home of their local rivals and their chances of breaking that sequence have been dealt a huge blow by the absence of top scorer Nicolas Anelka with a groin strain.

They do, however, have the memory of their unbelievable comeback in the previous round against Tottenham to fall back on and Keane acknowledges Kevin Keegan's City are probably not as bad as recent results suggest.

"The fact there will be 9,000 City fans there should ensure a brilliant atmosphere," said Keane, who has won the trophy three times with United and was a beaten finalist with the Old Trafford side and former club Nottingham Forest.

"We are all looking forward to the game and I'm sure their players are as well," he added. "Results-wise they aren't having a good time of it but I know one or two City fans and they say the performances haven't been that bad.

"There is a fine line between playing well and winning football matches and I'm sure City will be confident, especially when they look at the goals we have been conceding.

"But we are determined as well. The disappointments we have had in the FA Cup in the past few years make the competition more important to us than ever this season."