Borussia Dortmund players during a practice session on the eve of their Champions League tie against Arsenal, in Dortmund, on Monday. (AFP)

Berne: Barcelona start the defence of their Champions League crown at home to European veterans AC Milan on Tuesday unsettled by an injury to new signing Alexis Sanchez and a sloppy league display.

Pep Guardiola’s well-established side have already scooped the Spanish and European Super Cups this term, and are aiming for a fourth Champions League title in seven years, but looked unusually vulnerable in La Liga on Saturday.

The Spanish champions frittered away a two-goal lead to draw 2-2 at Real Sociedad as complacency took over and their trademark passing game deserted them in the second half. To rub salt in the wound, they lost new Chilean forward Sanchez to a torn hamstring that will keep him out for up to two months. “(Our morale) isn’t the best today,” Barcelona midfielder Sergio Busquets told a news conference on Sunday. “But we will react, and we will do it well and quickly.

The opening week of this season’s group stage features all the usual European soccer powerhouses with several mouth-watering clashes alongside the start of Barcelona’s defence of their trophy against seven-time champions Milan on Tuesday. Benfica host Manchester United in a repeat of the famous 1968 European Cup final, German champions Borussia Dortmund entertain Arsenal and Manchester City take on Napoli in a meeting of two debutants hoping to become regulars in the continent's premier club competition.

Bayern Munich, knowing they cannot afford any slip-ups if they want to take part when their Allianz Arena hosts the final, have a tricky visit to Villarreal and four-time European champions Ajax Amsterdam, hoping to reclaim their place among Europe's elite, host Olympique Lyon. After winning the Europa League with Porto last season, Andre Villas-Boas makes the step up to the continent's biggest stage when his new team Chelsea launches their campaign against Bayer Leverkusen on Tuesday.

Villas-Boas launches his attempt to succeed where his six predecessors have failed by delivering the Champions League trophy to Chelsea owner Roman Abramovich this season. Since the billionaire from Russia took control of the London club in 2003, Claudio Ranieri, Jose Mourinho, Avram Grant, Luiz Felipe Scolari, Guus Hiddink and Carlo Ancelotti have all left Stamford Bridge after failing to reach the Holy Grail.

In taking the job at Stamford Bridge this summer, Villas-Boas acknowledged that bringing European success to Chelsea was high up on Abramovich's wishlist. The closest Chelsea has come to lifting the Champions League for the first time was in 2008, when the team lost to Manchester United on penalties in the final in Moscow. Villas-Boas says, “Of course it’s a dream to everybody, but it's the most difficult trophy to win.”

Old romantics such as Uefa president Michel Platini are more likely to enjoy the meeting of Czech champions Viktoria Plzen and their Belarus counterparts BATE Borisov in Group H.

Plzen’s surprise qualification will be a tonic to Platini who has tried to open up the Champions League to smaller clubs with fewer resources and wants teams to have local identity rather than foreign imports.

Far from buying their way to success, Plzen have only four foreign players in their squad, all from neighbouring Slovakia, and stunned Czech football last season by winning their first league title with a team made up of promising youngsters and assorted journeymen.

The team revolves around 36-year-old playmaker Pavel Horwarth, who joined three years ago after he was no longer wanted by Sparta Prague and was voted Czech player of the year last season. The city is where Pilsner beer was developed in the 19th century although Vikotria will have to stage matches in Prague, around 90 kilometres away, as their own stadium is still not up to Champions League standards.

Tuesday’s matches
Group E: Chelsea vs Bayer Leverkusen, KRC Genk vs Valencia; Group F:
Borussia Dortmund vs Arsenal, Olympiakos vs Marseille; Group G: Apoel Nicosia vs Zenit St Petersburg, FC Porto vs Shakhtar Donetsk; Group H: Barcelona vs AC Milan, Viktoria Plzen vs BATE Borisov

(Agencies)