"I think they are the two teams that play the best football right now in the world," said New York Red Bulls forward Thierry Henry, who played for both.
Barcelona, the 2006 and 2009 champion, has outscored opponents 112-23 over 38 games in all competitions this season. Arsenal also embraces an attacking style of play.
"Tomorrow we want to be faithful to our philosophy. To make sure we dominate the game, that we pass the ball and that we have possession of the ball," Gunners manager Arsene Wenger said Tuesday. "If we do that, we have a very good chance of beating them."
The second-round matchup in the total-goals series, which concludes at Camp Nou on March 8, follows a quarterfinal meeting last year. The teams tied 2-2 at Emirates Stadium in the first leg, with Arsenal captain Cesc Fabregas breaking a leg, and the Blaugrana won the second leg 4-1 for a 6-3 aggregate victory as Lionel Messi dazzled with four goals, prompting Wenger to say "Messi's like a PlayStation."
Barcelona coach Pep Guardiola warned his players not to be overconfident.
"With Arsenal if you are not well prepared you will be chasing shadows," Guardiola said. "I like to watch Arsenal play football, but I don't like to play against them."
Barcelona had a team-record 28-game unbeaten streak earlier this season and won a Spanish league record 16 matches in a row before Saturday's 1-1 tie at Sporting Gijon.
"We will try and score a goal, because scoring away from home is very important," Guardiola said. "We want to bring at least a goal back to Barcelona."
Barcelona captain Carles Puyol will miss the game because of a knee injury, and a lack of height has made the Blaugrana relatively vulnerable to crosses into the penalty area.
But Messi, the two-time FIFA player of the year, has scored 40 goals in 34 games in all competitions this season, including 24 in the Spanish league.
"We need to be focused on the way we defend and not be focused on one man," Arsenal midfielder Abou Diaby said. "We know that individually he is really good, but if we do the job together I think it will be difficult for him. For me, that is the best way to control him and control the game."
Pedro Rodriguez has 19 goals for Barcelona's high-octane offense and David Villa has 18.
"The most important thing is to be well organized defensively and, when we have got the ball, play our game." Diaby said.
Arsenal's Robin Van Persie, finally over the left ankle injury that sidelined him from August until November, has 10 goals in his last seven games. Van Persie was sidelined for the games against Barcelona last year because of torn ligaments in his right ankle.
Arsenal's midfield has also been tougher defensively this season, and 19-year-old Jack Wilshere emerged as a gritty complement to captain Cesc Fabregas.
"They're a great team and very difficult opposition with very good players, especially up front," Rodriguez said, adding that the form of Fabregas and Van Persie will make it "a very difficult tie, different from last year as maybe they are more dangerous."
The Gunners beat Wolverhampton Wanderers 2-0 last Saturday, recovering from the previous weekend's embarrassment, when Arsenal took a four-goal lead at Newcastle only to draw 4-4.
Arsenal also hopes to be lifted by the return of Samir Nasri, who has been sidelined for two weeks with a hamstring injury.
"We don't deny the quality of Barcelona, but what is important for us is we have a good opportunity to show who we are now," Wenger said. "Not only that, we also want to show Barcelona we are capable of knocking them out."