Rome, Italy (My Sportsbook) - Barcelona and Manchester United are widely regarded as the two best teams in the world, so it is only fitting that they will meet at the Stadio Olimpico on Wednesday in the Champions League final.

Both sides have already clinched their respective league titles as well as a domestic cup, and both will be looking to cap memorable seasons with a win in Europe's most prestigious club competition.

For Barca, a win on Wednesday would allow them to become the first ever La Liga side to complete the treble, winning the league, Champions League and King's Cup.

United could also make a bit of history as they would become the first team to retain Europe's top prize since AC Milan claimed back-to-back European championships in 1989 and 1990, and they would be the first to do so in the Champions League era.

Barca will be looking to secure its third title, with the club last winning in 2006, while United is trying to win its fourth after beating Chelsea on penalties in last season's final.

Both are looking to make history but they are likely to go about it in a much different way, with the Spanish champions likely playing the role of the aggressor while United will rely on a world-class defense to slow Barca's potent offense and then look to counter attack.

The Barca offense is led by three extremely dangerous players in Samuel Eto'o, Lionel Messi and Thierry Henry, who have combined to score 71 goals in league play this season.

Add to that trio the play-making tandem of Xavi and Andres Iniesta in the midfield, and you have a nightmare of an evening for any defense.

Barca's attack has dominated La Liga this season with 104 goals in just 37 games, but they have looked much less formidable when matched up against the likes of United and Chelsea.

The Red Devils were able to keep Barca off the scoreboard over two legs in their semifinal meeting in the Champions League last season en route to a 1-0 aggregate win, while Chelsea held Pep Guardiola's side scoreless for over 180 minutes in this season's semifinals until a last-gasp goal from Iniesta sent them through.

It would appear that based on those two results, that Barca has trouble breaking down a well-organized defense, which is something that they don't see on a regular basis in the more wide open La Liga.

However, Xavi feels that even if United does sit back and defend, that his team must impose its style on the game if they want to win.

"Since I don't know what sort of game they'll play, what we have to do is get hold of the ball, dominate midfield and attack," Xavi said. "Winning means we have to impose our own style."

The problem for Barca is that if they do attack, they will leave a very thin back line open for counter attacks, which could play right into the hands of United.

The Catalan side will be playing without its two starting fullbacks as Eric Abidal and Dani Alves are both out through suspension, while central defender Rafael Marquez suffered a season-ending knee injury in the first leg against Chelsea.

This means that Guardiola will have some major shuffling to do along the back line, with the boss likely pairing midfielder Yaya Toure with Gerard Pique in the center, while captain Carles Puyol will be pushed out wide along with either Sylvinho or Martin Caceres.

The team selection of United boss Sir Alex Ferguson will also be watched closely because the side that he puts out on the field will determine how United decides to play.

It wouldn't be a big surprise to see Ferguson use a similar team to the one that beat Arsenal 3-1 in the second leg of its semifinal win.

That would mean leaving strikers Carlos Tevez and Dimitar Berbatov on the bench in favor of using Wayne Rooney and Cristiano Ronaldo along with Ji-Sung Park in attack.

United's lone injury concern is central defender Rio Ferdinand, who has returned to training after battling a calf injury, while midfielder Darren Fletcher will miss out because of a red card that he received in the second leg against Arsenal.

Both teams are capable of scoring goals but there are far fewer question marks surrounding United's defense, which will be the difference between the two sides and allow United to claim yet another trophy this season.