Football followers across Europe are preparing for another exciting dose of UEFA Champions League action this Tuesday and Wednesday, with three of the four quarter-final ties still very much in the balance.
Though Barcelona's 4-0 first-leg win appears to have put the contest beyond opponents Bayern Munich, Chelsea will still need to be wary of the visit of Liverpool despite their impressive 3-1 win at Anfield. Holders Manchester United, for their part, need a big performance in Portugal after being held 2-2 at home by Porto while Premier League rivals Arsenal cannot afford to relax despite picking up a valuable 1-1 draw at Villarreal's El Madrigal.
The big match
Porto - Manchester United (2-2), 15 April 2009, 20.45 CET, Estadio do Dragao, Porto
A difficult task awaits the Red Devils this Wednesday, with the European champions needing a win or a score draw higher than 2-2 to qualify for the last four. Manchester United failed to win on their three previous visits to Porto while the Dragons have won five and drawn six of a total of 11 previous home encounters against English opposition in Europe's elite club competition.
Added to the mix is the fact that United's previously imperious defensive line has conceded no fewer than 11 goals in their last five outings in all competitions and an attack that scored an average of 2.1 goals per game last season is averaging just 1.7 this campaign. Yet another dark omen for Sir Alex Ferguson's charges is that no winners of the European Cup or Champions League have retained their throne since AC Milan in 1989/90.
Porto, meanwhile, took full advantage of a comfortable 3-0 away win against Estrela da Amadora to further strengthen their position at the top of the league table as well as rotating their squad ahead of what promises to be an evenly contested second-leg encounter.
The other games
Chelsea - Liverpool (3-1)
Even in the absence of inspirational captain John Terry, last season's beaten finalists are in a very strong position ahead of the visit of Liverpool. In the sides' previous meetings in the competition, the Blues have never failed to progress when playing the second leg at home and will be buoyed by last season's 3-2 extra-time semi-final second-leg victory over Rafa Benitez's team at Stamford Bridge. That said, the Reds have won five and drawn two of their last seven away games in the Champions League proper.
The visitors can also draw strength from an overall record of 69 wins and 54 defeats in all competitions against Chelsea, though the west London outfit have won 42 and lost just 17 of these meetings in the capital. Boosting Liverpool's chances will be the return of tigerish midfielder Javier Mascherano, missing in the first leg, while Saturday's 4-0 win over Blackburn Rovers, which included a stunning opening strike from Fernando Torres, proved they have the firepower to hurt Guus Hiddink's team.
Arsenal - Villarreal (1-1)
An acrobatic leveller from Arsenal's Emmanuel Adebayor in the first leg could weigh heavy on a Villarreal side which now need at least one away goal. Already without midfield schemer Santi Cazorla for the rest of the season thanks to a fractured fibula, the Spanish club may now lose captain Marcos Senna for the second leg after the UEFA EURO 2008 winner strained a calf muscle in Saturday's 2-0 home defeat by Malaga.
The Gunners have injury worries of their own, particularly in defensive areas, with centre-back William Gallas ruled out for the remainder of the campaign and keeper Manuel Almunia and left-back Gael Clichy also unavailable.
Bayern Munich - Barcelona (0-4)
Despite the fact that a team have never previously overturned a four-goal first-leg reverse in the Champions League, and that Bayern Munich's own board of directors have claimed they would be satisfied with a mere consolation win, Jurgen Klinsmann's charges have not thrown in the towel. Their confidence boosted by a 4-0 Bundesliga win over Eintracht Frankfurt at the weekend, the Bavarian outfit need to go for goals against a Barcelona side boasting eight wins and three draws in their last 11 matches on their travels in the Champions League proper - a run including 13 goals in four away clashes this season.
"We're aware that a return match on German soil is never easy," said Barça midfielder Andres Iniesta. "We may have one foot in the semi-finals, but we can't play it until we have both feet there."
Player to watch
Manchester United's 17-year-old Italian forward Federico Macheda is the new darling of the Old Trafford faithful after scoring winners on both of his Premier League outings to date, against Aston Villa and Sunderland. His place in the hearts of the fans would be assured should he repeat the feat in Porto on what would be his Champions League debut.
23 - The number of matches Arsenal have gone unbeaten at home in the elite club competition. Their last home defeat dates back to a 2-1 reverse by Chelsea in the pair's quarter-final second-leg meeting in 2003/04. Indeed, the Gunners have conceded just seven goals in these 23 encounters and have yet to concede at home in this season's Champions League.
What they said
"Liverpool have won a Champions League final by scoring three goals in five minutes so we can score three times in 90 minutes," Liverpool defender Alvaro Arbeloa.
Have your say
Can Bayern Munich and Liverpool come back against all the odds? Will Porto spring the surprise of the round and knock out the holders?