Key players

Denil Son Arsenal v Roma

The Brazilian has played every minute of the Gunners' European campaign this year and assumes even more responsibility without Cesc Fabregas as his partner in midfield. Blessed with fine, close control and an eye for the incisive pass, the 21-year-old has grown in stature under the watchful eye of coach Arsene Wenger and seems to fit perfectly into the Frenchman's footballing outfit. However, he will be severely tested in Tuesday night's encounter against Roma at the Emirates, where he faces the tough-tackling Daniele De Rossi and the skillful Simeone Perrotta, an experienced duo on the big stage.

Cristian Chivu INter Milan v Man Utd

Having shone against AC Milan in last Sunday's crucial Serie A victory at the San Siro, the Romanian is now charged with the unenviable task of keeping United's rampant attack at bay on Tuesday. Away goals gain extra significance once the competition gets into the knockout stages and with Dimitar Berbatov, Wayne Rooney, Carlos Tevez and Cristiano Ronaldo in the opposition camp, the centre-back will have to be at his best. Should he keep the quartet quiet, Inter may prosper.

Fernando Torres Real Madrid v Liverpool

Liverpool go to a resurgent Real Madrid on Wednesday night without captain Steven Gerrard and will therefore rely heavily on 'El Nino' for that all-important away goal. The Spaniard had a superb European run last season, scoring six goals in 11 games as the Reds made it to the semi-finals before losing to Chelsea. However, Torres has endured a stuttering second season for the Anfield club because of a series of hamstring injuries, but three goals in his past two league games underline his importance to the side. Boss Rafael Benitez will likely employ a cautious approach, so the pace of his lone frontman must be utilised.

Mohamed Sissoko Chelsea v Juventus

If Claudio Ranieri expects to leave his old ground on Wednesday night with hopes of progression to the quarter-finals, much will depend on his Malian in midfield. The 24-year-old is often compared to Patrick Vieira, in that both share the ability to close down space and begin attacks from the centre of the park. Chelsea's strength is in that area, where Frank Lampard, Michael Ballack and Mikel form a formidable base from which to launch attacks. Sissoko will be key to stifling their influence on the game.

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