Manchester United are about to discover whether winning the Champions League this season is a practical proposition or an illusion due to be shattered by the realities of top-level European competition at the knockout stage.

Tonight, in the Louis II Stadium, United will face Monaco in the opening leg of their quarterfinal without Ryan Giggs, Gary Pallister and, in the longer term, Roy Keane. The fact that, despite losing players of this quality, they can still approach such an important match with relative equanimity is a testament to the speed at which the youthful caucus of Alex Ferguson's side has matured.

Not that youth is on United's side. In fact, the Monaco team Jean Tigana may field tonight will be slightly younger; average age 25, compared to the opposition's 26. Where Ferguson should have an advantage is in the collectively superior amount of competitive experience possessed by David Beckham, Paul Scholes, Gary Neville and Nicky Butt, who may well be United's most crucial player tonight.

The way Butt has taken over the midfield duties of Keane, out since the end of September with damaged cruciate ligaments, has been as important to Manchester United's progress this season as the new attacking partnership of Teddy Sheringham and Andy Cole. Add in the rise of Paul Scholes, following the retirement of Eric Cantona, and the feeling that 30 years after Matt Busby's United won the European Cup, the trophy may be about to return to Old Trafford is understandable.

In fact for some, the strength of Manchester United's performances during the group stage of the Champions League, especially the victories against Juventus and Feyenoord, has already made them favourites. 'That's rather ridiculous, given the enormity of the task,' Ferguson said yesterday, but unless United suffer a relapse here, the bandwagon will keep rolling in spite of the likely threats from Juventus and Real Madrid.

The Manchester United manager will have sufficient faith in his youngsters to play Butt, Scholes and Phil Neville in midfield against Monaco, much as he did at Chelsea on Saturday. But United are more likely to miss the speed of Giggs now than they did at Stamford Bridge and while Ronny Johnsen and Henning Berg will provide Norwegian solidity in central defence, it is a bad time to lose Pallister's mixture of command and composure at the back. Last season, Monaco's speed and mobility did for Newcastle United in the UEFA Cup and their pace will represent the greatest danger to English hopes tonight.

A knee injury has deprived Tigana of his most in-form striker, David Trezeguet. The Argentinian-born goal poacher, the second-highest scorer in France this season, has failed to recover, despite undergoing intensive treatment. However, his misfortune merely brings back the spectacularly-quick Thierry Henry, leading scorer in the Champions League this season, to partner Nigeria's Victor Ikpeba up front.

The task of restricting the influence of Sheringham should fall to Martin Djeto. Tigana described the England striker yesterday as 'a very intelligent footballer who regulates the whole team's play'. Philippe Leonard is expected to keep track of Beckham, who will also have to cope with the tackling strength of John Collins, the Scot who operates on the left side of Monaco's midfield.

The loss of Japhet N'Doram, their Chad midfielder, after a knee operation and of Trezeguet is threatening to disturb the balance of Monaco's team more than Manchester United's casualties will upset the equilibrium of Ferguson's side.

Against that, Monaco still have the means to overcome Manchester United with pace and technique if they get a good start. Their record in the group games was nearly as good as United's - four wins, a draw and a defeat, compared to five victories and one loss.

Tonight, Ferguson will not be looking for anything as spectacular as the Giggs-inspired 4-0 rout of Porto in the opening leg of last season's quarter-finals, the result that awoke people to the possibility of United winning the tournament, a notion dispelled by Borussia Dortmund, the eventual winners, in the semi-finals.

Yesterday, Tigana, who has just signed a new two-year contract with Monaco, diplomatically rated the chances of victory as 5545 in Manchester United's favour, while adding with a smile that 'in England, the odds against us are 16 to 1'. But avoiding defeat will be enough, for the moment, to keep Ferguson happy, particularly if United score an away goal.

Monaco (Probable): Barthez; Dumas; Sagnol, Konjic, Leonard; Legwinski, Djetou, Collins; Benarbia; Ikpeba, Henry or Trezeguet.

Manchester United (Probable): Schmeichel; G Neville, Johnsen, Berg, Irwin; Beckham, P Neville, Scholes, Butt; Cole, Sheringham.

Referee: M Diaz Vega (Spain).