FC Porto v Manchester Utd, Estadio do Dragao, 7.45, On TV: Net 2, Sky Sports 2: The sight of Richard Wilson, alias Victor Meldrew from One Foot In The Grave, boarding Manchester United's plane to Portugal somehow seemed appropriate given all the foreboding yesterday.

Where Meldrew goes there is usually something to be grumpy about, and the darkness of Alex Ferguson's mood was an accurate gauge of the team's disposition before a match that will test their depleted resources to the full.

Ferguson did not arrive at Oporto airport wearing a do-not-disturb sign round his neck, but he might as well have after being stung by growing criticism of his players. But, most of all, he has been increasingly agitated that a season of transition at Old Trafford has reached the "business end" with United seven points behind the leaders Arsenal in the Premiership, with Roy Keane alleging a culture of complacency among some of the younger players, and with legitimate concerns about the capacity of his defenders to withstand the talents of Europe's most accomplished attackers.

"I'm nae getting into that," was Ferguson's stock answer to questions about his team selection, the absence of Rio Ferdinand and the frequency with which defenders such as John O'Shea, Wes Brown and Quinton Fortune have been making rudimentary errors. "I'm not giving you anything," he proclaimed. "I'm not helping anyone here."

What did not need confirming, however, is that Ferguson's team cannot afford to make the type of defensive mistakes that have persistently undermined their title campaign since Ferdinand opted to begin his eight-month suspension in December rather than wait until his appeal is heard by an independent English Football Association tribunal, now scheduled for March 18th-19th.

Even without the injured Derlei, Porto have a reputation for being one of the most fluent attacking sides in Europe, with an outstanding playmaker in Deco and a wonderful talent in Carlos Alberto, a 19-year-old Brazilian who will be vying with the Lithuanian international Edgaras Jankauskas to partner Benni McCarthy in attack.

Ferguson has already described Porto as "the hardest draw we could have got" and in the brand-new Estadio do Dragao Portugal's serial champions will provide formidable opposition.

Uppermost in Ferguson's mind is whether he can afford to gamble on using Brown alongside O'Shea in the centre of defence. O'Shea's form has dipped dramatically from the audacious tyro who stood alone as the one United player to appear in every Champions League tie last season, a debut year most memorable for the nutmeg on Luis Figo at Old Trafford in April.

Even more worryingly for Ferguson, Mikael Silvestre's damaged ankle ligaments have elevated Brown to a level of increased importance when it has become clear over the past few weeks that he is struggling to find his form and fitness, having just returned from the fourth serious injury of his career.

"You don't like losing your best players," Ferguson said of Silvestre, "but Wes can only get better now, there's no question of that. It's not mental, just physical. Normally we give our players a programme of good training and reserve matches when they've been out with a long injury. Unfortunately, because of the Rio Ferdinand situation, Wes has had one hour in a friendly at Bristol City and then he was straight in the first team. So, realistically, we are asking an awful lot of the boy."

At least Brown is willing to admit his faults. The England international volunteered the information he requested extra training sessions to help his rehabilitation, accepting that he was "still not 100 per cent".

Some of the criticism that has come his way has been unjust but from whichever perspective it is far from ideal preparation, particularly when Fortune, at left back, hardly inspires confidence either.

One option available to Ferguson is to deploy Roy Keane in Brown's position, as he did against Juventus in Turin last season, but the manager is understandably reluctant to weaken his midfield. Instead it is likely he will play Keane and Phil Neville as holding players, with Ruud van Nistelrooy lining up as a solitary attacker and Louis Saha having to wait for his first Champions League start.

Ferguson, taking charge of his 100th Champions League tie, does not go along with convention that a 0-0 draw amounts to a profitable return. The priority, he said, is a clean sheet but he reckons United must get an away goal to establish themselves as favourites for the return leg.

He has also warned his players about Porto's reputation for having some of the most skilled divers on the continent, pointing out what happened when they played Celtic in last season's UEFA Cup final. Ferguson has enough problems without seeing his side lose to deception.

PROBABLE LINE-UPS

FC PORTO (4-1-3-2): Bruno; Ferreira, Costa, Carvalho, Valente; Mendes; Maniche, Deco, Alenitchev; Alberto, McCarthy.

MANCHESTER UNITED (4-2-3-1): Howard; G Neville, O'Shea, Brown, Fortune; Keane, P Neville; Ronaldo, Scholes, Giggs; Van Nistelrooy.

Referee: H Fandel (Germany).