Flynn's underdogs are cast in a new role

Part courtroom, part carnival, the fourth round of the FA Cup is set to be contested in an atmosphere that would have been inconceivable before Eric Cantona turned into Bruce Lee. Football faces a balancing act this weekend, nowhere more so than a t Old Trafford.

Manchester United's players would normally have been steaming adrenalin upon resuming their defence of the trophy against Wrexham. After two days in which children may have wondered if bete noire was French for United's change kit, and with every incident certain to come under national scrutiny, Alex Ferguson's team talk will have to tread a line between psyching up and calming down.

Events at Selhurst Park have increased the likelihood of the shock of the century, but only just. Already pleased to be avoiding Andy Cole, Mark Hughes or Steve Bruce, Wrexham must be praying the Double winners fall apart without Cantona, as Argentina did after losing Diego Maradona last summer.

Whether a side 13th in the Second Division are equipped to exploit the crisis is doubtful, although whereas United look to Paul Scholes, 20, for striking power, Wrexham boast Britain's top scorer. Gary Bennett, 32 goals this season, received such acclaimafter putting out Ipswich that his mother was stopped in a Merseyside superstore and asked for her autograph.

Bennett could be partnered by Steve Watkin, whose goal knocked out Arsenal three years ago, but Brian Flynn's goalkeeper, Andrew Marriott, will probably have more opportunity to inscribe his name in folklore as Wrexham strive to improve on the clubs' last FA Cup meeting. Thirty-eight years ago this weekend, the Busby Babes won 5-0 away and the crowd was bigger than the population of the North Wales town.

While those innocent days have gone forever, there is no shortage of games with the potential to repair, however temporarily, the game's reputation. Ten Premiership clubs travel and four cannot reach the last 16, with several big names at risk.

Take Chelsea, finalists last May, who make the short hop to Millwall, recent conquerors of Arsenal and Nottingham Forest, for a tie in which the behaviour of players and fans will be closely monitored. Or Everton, who go to reviving Bristol City without the suspended Duncan Ferguson and a paltry four away goals, all in London, to their name. And consider Tottenham, who will experience the Roker roar at Sunderland, whom they last met in the Cup en route to the Double in 1961.

Nor can Liverpool feel entirely confident about tackling Burnley on a surface likely to be treacherous after several days under snow. Remarkably, the Anfield side have not won an actual game in the Cup since Wembley in 1992, and the cunning of an old Evertonian adversary, Adrian Heath, will ensure that run is not ended without a struggle.

Wimbledon and Leicester might not be Goliaths but they are sure to be treated as such by the budding Davids of Tranmere and Portsmouth. Leicester's first away win, at Manchester City, has come just in time to send them south hopefully. The Dons, however,face a more arduous task at Tranmere, where they last played (and won) in the Fourth Division 13 years ago.

Any complacency Newcastle felt at the prospect of receiving Swansea ought to have evaporated after the Welsh minnows' victory at Middlesbrough. The Second Division Swans also boast a more recent Wembley pedigree - May's Autoglass triumph comparing favourably with Newcastle's 40 years without a win - but history and heart are unlikely to suffice.

Swansea went out to Nuneaton last season, so by tonight their manager, Frank Burrows, a player at Scunthorpe when Kevin Keegan was an apprentice, may see the merits of a respectable defeat and a major pay-day.

Leeds enter the fourth round in better shape than the third, in which they almost slid out at Walsall, but face a psychological barrier as well as Oldham. It is a sobering fact that they have progressed beyond this stage just once in 17 seasons; and thatGary McAllister, at 30, has never played in the fifth round.

Coventry, who beat Leeds to reach the 1987 final, have a similarly wretched record since taking the Cup. The Sky Blues are in the fourth round for only the third time in the ensuing years, and meet Norwich four days after their 2-2 draw in Norfolk knowing they have yet to go further.

By coincidence, two of the other three all-Premier ties are also "replays" of close-fought League encounters. After sharing four goals on New Year's Eve, Manchester City and Aston Villa reconvene at Maine Road, where the heat will be on Brian Horton should City fail again. Meanwhile, Forest entertain Crystal Palace, 1-0 losers at the City Ground this month.