A boyhood Celtic supporter in Dalkeith, Fletcher, 24, takes his devotion to the club to which he has been attached for the second half of his life to extremes that belie the notion of the gap between players and punters having become a chasm.

"I've turned into a right fan," he says of his time on the casualty list. "I've been up in the stand, shouting like a lunatic. It has just come over me and I've got really involved. The Glazers (United's American owners] must think I'm a right one!

"I'm breaking the etiquette in there (the directors' box]. Everyone cheers when United score, but they don't stand up like I do to shout at the referee when there's a dodgy penalty against us, or when the Arsenal players are surrounding Cristiano Ronaldo as he's about to take a penalty."

They sound like the confessions of a naughty schoolboy, which is appropriate since Fletcher is speaking immediately after addressing a hall full of 11 to 16-year-olds in Q&A session at Sale Grammar School in the leafy suburbs of south Manchester.

Subduing Lionel Messi and Thierry Henry would be a doddle after interrogation by Year 7's sharpest football brains at an event organised by Scotland's team sponsors, the Nationwide Building Society. One girl asks whether he ever misbehaved in class. "I had my moments," Fletcher replies, going on to explain that his mother, clearly a motivator in Sir Alex Ferguson's class, warned him he would not be signing for United unless he passed his exams.

When his team-mates face their sternest tests in the pursuit of a Champions League and Premier League double, visiting Camp Nou on Wednesday and Chelsea a week today, Fletcher will again take literally his supporting role. A month after scoring twice in the 4-0 FA Cup rout of Arsenal – the day Arsene Wenger's side were stripped of their irresistible aura – he suffered a knee injury in the 89th minute of Scotland's friendly against Croatia at Hampden.

However, the man Ferguson hails as "a big-game player" is confident of resuming active service well before May 21 in Moscow and the possible opportunity to lift the European Cup. "I'll be back any day now," says Fletcher. "I'm not setting a target, but I've been doing a lot of running and ball work. There's a lot of games left so I've got to try to get in contention as soon as I can, though the lads are all performing so well that it will be hard to get a game."

United trounced Roma in last year's quarter-finals only to be soundly beaten by AC Milan when the club's third final was within reach. Roma have been dispatched again, and Fletcher trusts United's chastening semi-final experience will stand them in good stead. "You learn much more from disappointments than from wins. As a team, we didn't really turn up at San Siro.

"The Barcelona matches have the potential to be cagey affairs. They'll certainly start that way. We won't be going out there on all-out attack. But the advantage for us is that unlike last season, we've got the second leg at home. There's a lot we want to rectify from last year.

"It's all about getting to the final. There's more than one way to win a match and I've seen both ends of the scale. Teams come to United and get 10 men behind the ball to make it difficult for us. I've done exactly the same for Scotland in France and Italy, when we scrapped and fought for every ball, and I enjoy those victories just as much. We may need a Scotland performance to get to the Champions League final."

A few Manchester United displays would not go amiss when the Scots hit the World Cup trail in September. Fletcher, who has captained his country three times, looks forward to pitting himself against top-class opposition in the next international friendly, against the Czech Republic in Prague on May 30.

"It's a good game to have, because we'll learn from it. There's no point playing teams you can beat 4-0. That's why the draw with Croatia in George Burley's first game was so credible. The new manager has come across as really enthusiastic and positive. We've had some changes at the top but the continuity is there in the squad. We're looking to pick up where we left off against Italy. Not result-wise, obviously, but in the momentum we gained and the progress made.

"We've had a great couple of years and there's real competition for places. Walter Smith laid the foundations for us to be resilient and organised. Under Alex McLeish we got better at keeping the ball and making things happen. It's difficult: you go from Scottish football, which is 100mph, to the Continental game, where you've got to slow it down. But I think we just need a bit of tweaking (from Burley] to get to the next stage."

James McFadden left Everton for McLeish's Birmingham in search of a regular club game. With such a wealth of engine-room talent at Old Trafford, Fletcher is often tipped to follow suit, but dismisses the idea that the grass is necessarily greener elsewhere. "There have been great midfielders here before – Nicky Butt, Roy Keane – but it's all a challenge to me.

"I didn't play as much as I'd have liked in the first half of the season because of the great form of Paul Scholes, Michael Carrick and Anderson. But I didn't let my head drop. I thought, 'I'm going to work harder, and take my chance when it comes'. If you're grumpy and moaning, you're no use to anyone. And I feel part of United."

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