Clashes between Liverpool and Chelsea have become something of a Champions League normality. The two teams are about to meet for the fourth consecutive year in the competition and the third time at the semi-final stage.

This last-four contest with a Premier League flavour has traditionally given rise to cautious encounters (3 goals in 6 matches), with the Reds of Liverpool emerging victorious in both 2005 and 2007. But this year, there is one small factor that could help tip the balance from red to blue. The group stage encounters in the 2005/2006 season apart, this is the first time that Chelsea will be playing the return match at their home fortress, Stamford Bridge.

Unbeaten at home in the Champions League since Marseille triumphed 1-0 at Anfield on 3 October 2007, Rafa Benitez's charges went on to finish second in Group A before overcoming Inter Milan in the Round of 16 (2-0, 1-0) and Arsenal (1-1, 4-2) in the quarters - a run of seven European games without defeat. Winners of 11 of their 14 European semi-finals to date (on route to five European Cup/Champions League and three UEFA Cup successes), Liverpool clearly have the edge in terms of continental pedigree.

Having had their dreams of Champions League glory snuffed out at the semi-final stage three times in the last five years, Chelsea are the only club in the final four never to have won the competition. This season, the Blues finished top of Group B before curtailing the exploits of the tournament's two surprise teams, Olympiacos (0-0, 3-0) and Fenerbahce (1-2, 2-0).

Another important factor could be the varying commitments of the two clubs. Liverpool lie fourth in the Premier League and are practically assured of qualifying for the competition again next season, so nothing should distract them from this semi-final. Chelsea, however, are only three points behind Manchester United and play host to their rivals on Saturday in what could prove to be the title decider. So while Liverpool are sure to rest certain key players, Avram Grant cannot afford to rotate his squad, though the Blues do have the kind of strength in depth suited to such an intensive programme.

Key contests
Despite the presence of strikers with the pedigree of Fernando Torres and Didier Drogba, it is instead the duel between Claude Makelele and Steven Gerrard, the two players who have played in all their sides' Champions League fixtures this season, which is likely to set the tone of this encounter.

Gerrard is the driving force, as well as being his side's top scorer this campaign with six strikes and the provider of four assists. A tireless ball-winner, Makelele is the metronome of the slick Chelsea mechanism. On Tuesday, he will be appearing in his eighth Champions League semi-final, a record he has set with three different clubs (Nantes, Real Madrid and Chelsea), although he has tasted victory only once (Real in 2002). Makelele and Chelsea will also have to cope without the suspended Michael Essien.

The words
"Steven Gerrard is a great player and a great person. For me he is the player of the season in England and maybe in Europe because of the influence he has on his team. He's an example for everyone. Even though he's one of our opponents, he's still my favourite player." Avram Grant, Chelsea coach

"Our fans are more obsessed with winning the championship than the Champions League. We haven't won the league title for 18 years, but I believe it will come. Personally, I'd love to play in a Barcelona-Liverpool final." Fernando Torres,Liverpoolstriker

Past Champions League meetings
Semi-final 2004/05 season:
27 April: Chelsea 0 Liverpool 0
3 May: Liverpool 1 Chelsea 0

Group Stage 2005/06 season - Group G
28 September: Liverpool 0 Chelsea 0
6 December: Chelsea 0 Liverpool 0

Semi-final 2006-07
25 April: Chelsea 1 Liverpool 0
1 May: Liverpool 1 Chelsea 0. (Liverpool won 4-1 on penalties)