"No problem … No problem." Cristiano Ronaldo repeated the phrase over and over as he reflected on the penalty miss that prevented Manchester United FC leaving the Camp Nou with the priceless away goal that would have swung their UEFA Champions League semi-final tie against FC Barcelona firmly their way. As the press clamoured to speak to the 23-year-old after the goalless draw he did not duck away, facing them with a smile, displaying the confidence that has done so much to take United to within one victory of a third European Champion Clubs' Cup final.

'Always confident'
"Sometimes you score, sometimes you don't. I missed a penalty, no problem," he said. "I'll try to score in Manchester. I'm always confident. I have 38 goals this season. It is not a problem if I miss one or two. I try to do my best every game. Since I have been in Manchester I have scored 15 or 16 penalties I think and missed two. I don't think it's a problem. No one has said anything to me because I always try to score, to play well. Today I missed a penalty, no problem. In Manchester if I have another penalty I will try to score again."

Frustration
It was a rare night of frustration for the Portuguese international who has led United's charge towards a domestic and European double and heads the UEFA Champions League scoring chart with seven goals. A game that started so promisingly for him when Gabriel Milito handled his header in the area soon turned to anguish as he fired the resulting spot-kick wide of Víctor Valdés's left post. From then on little seemed to go right for player widely tipped to succeed Kaká to the Ballon d'Or. While Lionel Messi ran at will at the United defence, Ronaldo was starved of possession.

Torrid evening
When the ball did come his way, he was buffeted and bruised between the Barcelona centre-backs Milito and Rafael Márquez. The latter had a torrid evening trying to contain him. Booked for one cynical block, he might have conceded a penalty with another after Andrés Iniesta had errantly slipped the ball into the forward's path on the edge of his own area. The sight of Ronaldo, kneeling on the Camp Nou turf, hands pointing to the heavens after being clattered to the ground again midway through the second period summed up his evening.

Chelsea test
With crucial games coming thick and fast, though, starting with Saturday's potential title-decider against Chelsea FC, Ronaldo will not be down for long. He has made a habit of thriving in adversity. After his run-in with United team-mate Wayne Rooney in the quarter-finals of the 2006 FIFA World Cup, which led to the England striker's dismissal, it was feared he might be hounded out of the English game. Instead he responded with 17 Premier League goals to help United win the title. His 28 league goals this term have put United on the cusp of reclaiming their crown.

Cantona reminders
The bravado and confidence with which Ronaldo plays is reminiscent of Eric Cantona, himself no stranger to adversity. After eight months out after assaulting a fan during a match against Crystal Palace FC in January 1995, the Frenchman returned to help United overhaul a 12-point defecit against Newcastle United FC to win the title. Like Ronaldo, Cantona gave United a swagger, a belief that nothing was impossible. There is something provocative, intimidating, in the manner in which Ronaldo stands over a free-kick, chest puffed out, square on to the ball, pausing to stretch out the drama before unleashing a dipping, swerving and often unstoppable shot.

'Frightening'
Cantona, though, never took United to the UEFA Champions League final. Ronaldo will get the chance to do so on Tuesday. Outshone by Kaká as Milan brushed United aside at this stage last season, the winger is in no mood to be bossed about again. Ryan Giggs, the one United player on Wednesday who also featured in his side's 1999 UEFA Champions League victory at the Camp Nou, is convinced the 23-year-old's time will come. "It's rare to get a player who is at his top form for so long, for over two years," Giggs said. "Last season he just carried on into this season and his goalscoring record is just phenomenal for a winger. To score that amount of goals is frightening. I think he can get better, he can improve and he will do."

'Play better'
Starting in Manchester on Tuesday. "We are at home, we will have 75,000 people behind us," Ronaldo said. "It's going to be different, we will try to play good football and try to win. I think we'll create more chances in Manchester but it will be a different game and I'm sure we're going to play better." No problem then.

Whatever else Chelsea FC and Liverpool FC might produce when they conclude their UEFA Champions League semi-final it is unlikely they will give us a glut of goals.
 
'Cancel each other out'
The seven previous contests between the Premier League rivals in the competition have produced an average of 0.7 goals per game and the message from former Liverpool defender Mark Lawrenson is we should expect more of the same next Wednesday night. "Chelsea and Liverpool completely cancel each other out," he told uefa.com. "The first leg was probably the game with the most chances for a long, long time between the two of them and there weren't many. I don't think your 'match-winners' will win between Liverpool and Chelsea, it is the team who makes fewer mistakes."

Philosophies
The 1-1 first-leg draw at Anfield was the highest-scoring game between the teams in the UEFA Champions League – the previous six had yielded just three goals – and Lawrenson, a European champion with Liverpool in 1984, said the tight nature of these encounters was inevitable given the attitude of the managers involved. "If you look at both managers, the philosophy of football is they are both steady – [Rafael] Benítez and [Avram] Grant, their glass is always half-empty, it is never half-full. You are either an attack-minded manager or a defensive one and they are the latter." 
 
More positive
Liverpool may have to alter their usual approach, however, given their need for an away goal at a ground where they have not found the net in eight previous visits under Benítez. Lawrenson believes they will get one too. "I can see 1-1 at Stamford Bridge," he said. "There is no bias in that – Chelsea aren't playing well at the moment. I can see Liverpool scoring."

'Liverpool will have a go'
He is not alone in expecting the Merseysiders to pose a greater attacking threat, with former Chelsea winger Pat Nevin telling uefa.com that he expected a livelier affair than the teams' most recent meeting at Stamford Bridge in the Premier League, which finished 0-0 in February. "I was at the last game at the Bridge between Liverpool and Chelsea and I stayed awake for most of it," he joked. "It was one of the most boring games I have ever seen. The two best players were the two central midfielders but it won't be like that this time, because Liverpool will have a go."

Čech key
Nevin, who spent five years at Chelsea in the 1980s, considers the Londoners slight favourites to advance to the final in Moscow, basing his assessment on their excellence in defence. The former Scottish international cites the importance of goalkeeper Petr Čech and defender Ricardo Carvalho, both of whom made key contributions at Anfield, Čech with saves from Fernando Torres and Steven Gerrard and Carvalho with his lightning-quick covering at the back.

'Good chance'
"I will go for Chelsea because Čech is fit and Carvalho is fit," said Nevin. "Carvalho is the best defender for me in the world at the moment. His reading of the game, his tackling, the timing is amazingly good, I remember a couple of times at Anfield where he came across to cover John Terry. You don't realise how fast he is. He has got virtually everything in his game. The fact they have that core defensively and that Michael Essien will be back from suspension means Chelsea have a good chance."

Ninety-eight thousand came to the Camp Nou expecting a semi-final thriller. Millions tuned in around the globe. The night was electric, the talent sublime and the stage set. Manchester United FC manager Sir Alex Ferguson had predicted a fixture fit for UEFA Champions League final in Moscow. Then the unpredictable happened. Amongst the scintillating play, nerves hit, and they hit hard.

Form book
Perhaps it is a small part of the beauty of top level sport, in particular the UEFA Champions League, that only its unpredictability is absolutely certain. The form book may speak so loudly ear plugs are needed to ignore it, thousands of fans can travel to watch their team more in hope than expectation, but then nerves gnaw away at the performances of footballers who have seen and done it all before. How else to explain Gabriel Milito's waving hand, right in the middle of his own area, which gave away the second-minute penalty? More remarkable still was the effort which followed when Cristiano Ronaldo, indisputably the world's most in-form player, failed even to test Victor Valdés from the spot, placing his kick wide of the goalkeeper's left-hand upright.

Nervous tension
Unfortunately for the United forward, his miss only redoubled the nervous tension in a young man who had previously looked capable of winning this most cherished club competition virtually single-handedly. While he simmered and stewed, caught in the kind of private torment which only those who have fluffed their lines in front of almost 100,000 onlookers can understand, others caught the bug. How else to explain Edwin van der Sar being gently pressed by Samuel Eto'o and Andrés Iniesta in the 12th minute and instead of kicking the loose ball out of harm's way, sending it directly to the permanently menacing Lionel Messi?

Excellent Iniesta
Barça were not exempt either. The otherwise excellent Iniesta slid a thoughtless pass directly across his own penalty box, Ronaldo surged forward to meet the chance and although referee Massimo Busacca this time declined to point to the spot, Rafael Márquez's challenge was all desperation and no elegance. Perhaps these superstars deserve a trifle more understanding and empathy at times. The salaries are high but they train, rehearse, plan and hone their bodies to perfection – then at the vital moment they can commit an error they have not been guilty of since the school playground. 

Superb outfits
The more these two superb teams probed and tested, like two powerful middleweights wary of the other unleashing a thumping right hook, the more you had to feel sorry for John Arne Riise's calamitous moment the previous night at Anfield. Tension bites hard when Europe's premier club competition reaches this stage. 

Voracious hunger
Carlos Queiroz waved Ronaldo forward and the player snapped back, all flailing arms, that he could not even get a touch of the ball. Before the end, the Portuguese had sniped at Rio Ferdinand, prayed to the heavens and showed voracious hunger to atone for that one inexplicable moment at the start of the match. But no one should be too hard on him, or Riise. They willl hide their pain, patch up their frayed nerves and stride back out for battle again next week. And expectation, anticipation and the prize at stake will be just as high second time around.

Pierluigi Collina may have retired from refereeing two years ago but he remains one of the most respected figures involved in the game. The 48-year-old refereed the 1999 UEFA Champions League final and the 2002 FIFA World Cup final and now works for the Italian football league and is on the UEFA Referees Committee. Here he looks back on a remarkable career and discusses what it takes to be a successful referee.

When did you start refereeing?

Pierluigi Collina: A long time ago. I was 17 and I did it without any reason, only because my friend at school went on a referee course and asked if I wanted to go along.  I said, "Why not?"  I certainly wasn't convinced I would be here talking about refereeing more than 30 years later.

What was the most memorable match you've refereed?

Collina: I've been very lucky as there have been many great matches. I have to mention the World Cup final – for players, coaches, referees and even TV commentators it's fantastic to be involved. To be one of the referees is to be a part of football history. I was also the referee of the Champions League final in Barcelona between Bayern Munich and Manchester United. Two goals were scored in stoppage time which must be one of the most memorable ends to a football match. I also refereed England v Scotland at Wembley. That's an exciting match, as was Real Madrid v Barcelona in the semi-finals of the Champions League which I also did.

Which team did you support as a boy?

Collina: It's normal for a kid to support a team, but a referee needs to be professional like a player – sometimes a player will play against a team they supported but because they are professional they try to do their best. It's the same for a referee. If you don't want a referee who supported a team when they were a kid then you need to bring them in from Mars or another planet!

How do you maintain authority with players?

Collina: It's a matter of respect. You need to be accepted not because you are the referee but because players trust you. You achieve the best results when you're accepted. Even when you are wrong and players maintain that trust.

Have you heard about the "Respect" campaign in England?

Collina: I read something in the newspaper and I think respect is the key word, even for EURO 2008. Respect means a lot of things – for your opponents, for yourself, for your health, for the fans as they enjoy the show. For everyone, even the referee so I'm very happy you use this word because I consider it key for the future of the game. It's not just a matter for referees. The issue is important but everyone needs to contribute to solve the problem.

What do you need to be a good referee?

Collina: It is very difficult to say. There is not one tip to be a good referee. It's about preparation. You can achieve a good level with this. Some years ago running and knowing the rules was enough but these days you need to find more information and knowing football – the culture, understanding players. There is no one way to referee. I don't have a style. When I was growing up I tried to get something from everyone. Learning and understanding each other is important on the field, it's part of the respect I talked about earlier. The worst thing that could happen on the field is when referees and players consider themselves enemies. Perhaps that's the wrong word, but the opponents are the two teams. The referee isn't involved, he must help them. 

Did you try and get in the minds of the players?

Collina: If you wish to be accepted you need to be understood and to do that you have to understand. That's why it's not about authority, it's about accepting because you understand I'm doing my best. 

Collina is an ambassador for the Castrol Performance Index which analyses the performances and effectiveness of players competing at UEFA EURO 2008™.