With 20 UEFA Champions League semi-finals appearances between them, not to mention seven finals and four titles, Manchester United and Barcelona are two of European football's biggest hitters. And on Tuesday night, the duo will slug it out for a place in the 2008 final.

Yet to suffer defeat in this year's competition, the Red Devils and Barça were both beaten in their respective weekend league engagements. As a 2-1 loss to closest challengers Chelsea showed, the end-of-season pressure could well be getting to Sir Alex Ferguson's men as they chase down a 17th league title. Over in Spain, meanwhile, Barcelona have given up the ghost in La Liga and sent out an under-strength side against Deportivo La Coruna, with the Galicians sauntering to a 2-0 win.

Recent form aside, both teams are packed with genuine entertainers and after last week's hard-fought stalemate, the tie could turn on a flash of individual brilliance. Strangely, though, these two attack-minded units are finding goals hard to come by as the season approaches its finale, with physical fatigue no doubt playing a part in that. Cristiano Ronaldo's penalty miss at the Nou Camp could prove vital, and being a keen statistician, Ferguson will know only too well that United failed to progress on the last three occasions they played out goalless draws in first legs away from home.

Frank Rijkaard's charges just need a score draw to reach the final, although United's form at their Old Trafford fortress is impressive to say the least. The English giants have won their last 11 matches in the competition there, and in 16 home outings against Spanish opponents, the two-time European champions have won seven, drawn seven and lost just two. As for the Spaniards, the only two reverses in their last 32 matches in the tournament came against English sides - Chelsea and Liverpool.

Statistics are one thing, but form and momentum are quite another. While Barcelona have been boosted by the recent return of Lionel Messi, United have expended a significant amount of energy on their recent domestic commitments, and still face decisive encounters with West Ham United and Wigan Athletic as they bid to hold off a confident Chelsea side in the Premier League.

Key contests
Last week's first leg saw Lionel Messi came out on top in his private duel with Cristiano Ronaldo, and the second showdown between the two will be vital to the outcome of Tuesday's return leg. The threat of suspension for May's final could also have an influence on proceedings. United trio Patrice Evra, Owen Hargreaves and Nani are all a booking away from missing out on the Moscow showpiece, as are Gabriel Milito, Yaya Toure and, perhaps most importantly of all, Messi for Barcelona. One man suspended from duty on Tuesday is Mexican defender Rafael Marquez.

The words
"I'm convinced the second leg is going to be a different game and that we'll play better. I think we'll go through because I'm going to score in Manchester." Cristiano Ronaldo, Manchester United winger

"It's not easy to play at home when you've drawn 0-0 away in the first leg. When you've got a team that plays as well as we do and which has so many players who can score, you're pretty sure the ball's going to go into the back of the net. If we can play the way we know we can play, there's no reason why we can't go through." Samuel Eto'o, Barcelona striker

Past Champions League meetings:
Group stage, 1994/95 season:
19 October: Manchester United 2-2 Barcelona
2 November: Barcelona 4-0 Manchester United

Group stage, 1998/99 season:
16 September: Manchester United 3-3 Barcelona
25 November: Barcelona 3-3 Manchester United

Semi-final, first leg, 2007/08 season:
23 April: Barcelona 0-0 Manchester United