LONDON (AP) – Seeking a third Champions League title in four years, Barcelona will again be the team to beat when Europe's elite club competition kicks off this week.
Led by Lionel Messi, the Spanish giants produced a football clinic to dispatch Manchester United 3-1 in last season's final at Wembley and few would bet against them being anointed European champions for a fifth time in May's showpiece at Munich's Allianz Arena.
''They are so difficult to play against,'' said United striker Wayne Rooney. ''It is hard to get the ball off them and when you do, you are tired from chasing around.
''You have to applaud them for the way they play. They are a great team to watch. Our aim for us to reach that level over the next few years.''
Fierce Spanish rival Real Madrid, English sides United, Chelsea and big-spending newcomer Manchester City plus Italian champion Milan are among the main threats to Barcelona this season.
And it's at home against Milan, a seven-time European champion, where Barcelona begins the defense of its title in a repeat of the 1994 final, which the Serie A team won by dishing out a memorable 4-0 thrashing.
Barcelona is Europe's superpower 17 years on, however.
Pep Guardiola's side has already won two trophies this season - the Spanish Super Cup and the European Super Cup - and is bidding for a 10th victory in its past 11 home games in the competition.
Milan hasn't been beyond the competition's last 16 since 2007, the year it won the last of its European titles.
''They have great players, especially in attack with (Zlatan) Ibrahimovic, (Alexandre) Pato, Robinho and (Antonio) Cassano, and we have to pay a lot of attention to them,'' said Barcelona midfielder Sergio Busquets.
Of the first timers, Man City looks likely to be the one to break up the established order.
Backed by the bottomless pockets of Abu Dhabi billionaire Sheikh Mansour, City has built a squad that is the envy of most clubs on the continent and has won all four of its matches in the Premier League this season. With options in its forward line comprising Carlos Tevez, Sergio Aguero, Edin Dzeko, David Silva and Samir Nasri among others, they could make a splash back in Europe's elite for the first time since 1968.
''This a new season, a new era,'' said England defender Joleon Lescott, who is among the raft of expensive recruits brought in by City over the past two years. ''We've got new signings and once everyone is together and firing on all cylinders, I'm sure we will be there or thereabouts.''
Spanish heavyweight Real Madrid, the competition's most successful team with nine titles and coached by two-time winner Jose Mourinho, visits Dinamo Zagreb in Group D, which also sees Ajax host Lyon on Wednesday.
Madrid was eliminated by Barca last season after an explosive pair of semifinal legs but with Mourinho appearing to be adopting a more attacking philosophy, the capital club - led by star forward Cristiano Ronaldo - could be even more dangerous.
''(The Champions League) left a bad taste in our mouths,'' Madrid goalkeeper Iker Casillas said. ''We hope to take a step forward in our quality of play and arrive to the same point as last season.''
Elsewhere, United, which is top of the English Premier League, visits Benfica on Wednesday in Group C, which also includes Basel and Otelul Galati. The other matches that night are in Group B, where 2010 champion Inter Milan hosts Trabzonspor and Lille is at home to CSKA Moscow.
On Tuesday, Arsenal travels to Borussia Dortmund and Olympiakos hosts Marseille in Group F, while Chelsea is at home against Bayer Leverkusen and Valencia visits Genk in Group E.
In Group G, Europa League champion Porto hosts Shakhtar Donetsk, a Champions League quarterfinalist last year, and Apoel Nicosia is at home to Zenit St. Petersburg.