Key clashes: Three duels which can decide Manchester United v Chelsea

Nemanja Vidic v Didier Drogba It is nearly three years since Didier Drogba last scored against United – even if that goal did settle the 2007 FA Cup final – but he is still a great danger. Nemanja Vidic, who is settling down and showing that he has regained the fitness needed to appear regularly, has the strength to match the Ivorian. Drogba, however, also has moments of great dexterity and explosiveness. The defender will hope to cause the sort of frustration that can see this attacker lose his focus. Patrice Evra v Paulo Ferreira Paulo Ferreira, the Chelsea right-back, has started only seven Premier League matches this season and four of those have come since 13 March, because of injuries to others. His experience is undoubted but Carlo Ancelotti does not normally favour him. United will surely use the overlapping Patrice Evra and others to try to expose a potential weakness on that flank. The Frenchman is not especially flamboyant, despite being a winger in his youth, but his work-rate and all-round ability mean that he will help put pressure on Ferreira. Dimitar Berbatov v John Terry Gladness in Chelsea's ranks over Wayne Rooney's absence must be offset by the knowledge that his replacement has outstanding touch and vision. Dimitar Berbatov has enough sinewy force not to be bullied by John Terry and his movement may make him even harder to track than Rooney. The Bulgarian's ratio of goals to games has been impressive this season, but the challenge is to show that a sometimes laconic individual can be a key performer on an occasion of this magnitude.