Manchester United boss Sir Alex Ferguson feels his side's Champions League quarter-final against Roma is the toughest of all the last-eight ties.
Led by their talismanic striker Francesco Totti, the Italian side shocked Lyon with a 2-0 win in France in the last round and are confident of continuing their progress.
United travel to the Stadio Olimpico for the first leg on Wednesday before the return at Old Trafford on 10 April.
Roberto Maida, who covers Roma for Italian newspaper Corriere Dello Sport, explains how the tie will be won and lost.
GREAT EXPECTATIONS
It is unusual for Roma to get this far in this competition. It is the first time they have been here since the Champions League format began.
They are second in Serie A but they have lost sight of Inter, who are leading by 20 points, so everything at Roma is focused on the Champions League now.
They did not have a very good time in the competition this season until the win in Lyon - but that has brought it to life for them.
Fans queued for more than 24 hours to get tickets for the game against United and many still did not succeed.
After Lyon everybody here was convinced that Roma can win the Champions League.
United are fascinating opponents but nobody is scared of them. Roma will respect them, of course, but they do not fear them.
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For Roma's coach Luciano Spalletti and his players, this is the game of their lives.
THE TOTTI FACTOR
Of course, he was a world champion with Italy last summer but he has won only one championship with Roma in his club career.
This season has been his chance to show his skill on a wider stage with his own club and he has been in superb form.
He is the highest goalscorer in Italy at the moment, with 18 goals in 28 Serie A games, and he has never led the standings before - and in Europe he has been scoring regularly too.
But he is an unusual striker because he moves a lot from the front. He comes to midfield to take the ball and sometimes he is more valuable as a creator than as a goalscorer.
For example, against AC Milan on Saturday he never looked dangerous in front of goal but he still did so much good for the team.
He put Simone Perrotta clean through with an amazing trick. He made something incredible and that is his strength - in one second he can create something that can change a game.
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This is a chance for Totti to show the world that he was right to link himself to his home club for life.
ROMA'S ATTACKING THREAT
Lyon felt they were sure to beat Roma easily and that was their big mistake.
They accepted the first leg in Rome with no goals because they were sure they could destroy Roma in Lyon.
But if you face Roma with an attacking approach and without considering their counter-attacking threat then you risk a lot.
Roma love to play on the counter-attack, with the speed of players like Simone Perotta, Alessandro Mancini, Rodrigo Taddei and Totti. They have a lot of fast players who can create problems.
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The win in Lyon was something of a consecration for the team and Spalletti's style.
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STOPPING RONALDO
Max Tonetto is the left-back who was supposed to mark Ronaldo when he is on the right side.
He has a hamstring injury and is not available for the first leg - and maybe won't recover for the second game either - so Christian Panucci, who is a good defender, will look after him on that flank.
But if he plays on the opposite side he will find Marco Cassetti, who is used as Roma's first-reserve defender.
Cassetti is not such a good player. He lacks some experience, especially in European games, but he played well in Lyon in the previous round so Spalletti is confident he will do well against United.
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Roma are expecting Ferguson to switch Cristiano Ronaldo from the right wing to the left during the games. They know stopping him will be very important.
CAN ROMA BEAT UNITED?
But they will be in a difficult situation on Wednesday because they are missing a lot of defensive players through injury.
Roma's best chance will be to attack. They need to make the most of United's problems and take a little advantage for the second leg - because at Old Trafford it will be very difficult for them.
United play much better at home but, most important of all, is the fact that only a few Roma players have played at Old Trafford before and they could find it intimidating.
So to have a chance of progressing, Roma need to win the first leg at least 1-0 or 2-1.
They cannot rely on the counter-attack as much as they did against Lyon because Ferguson knows exactly how Roma will try to play.
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Player for player, United are stronger and superior technically.