Barcelona coach Pep Guardiola and Arsenal manager Arsene Wenger will be forced to alter their starting lineups because of injuries and suspension.

Barcelona is without striker Zlatan Ibrahimovic and center backs Gerard Pique and Carles Puyol, while Arsenal is hurting even more with a handful of starters missing, including captain Cesc Fabregas and Andrei Arshavin.

Following the 2-2 draw in the first leg, Arsenal will need to go for victory since the European champions hold the away-goal advantage.

“We will need all the spirit we have,” Wenger said.

“The problem we have at the moment is that we are short.” Both teams will take momentum from league wins on Saturday, with an under-strength Barcelona rolling over Athletic Bilbao 4-1 and Nicklas Bendtner's injury-time goal earning Arsenal a 1-0 win over Wolverhampton Wanderers. But Barcelona appears to be in better health than its Premier League counterpart going into the second game of what has been a thrilling matchup so far.

Fabregas broke his leg scoring the equalizing penalty in the first leg, although the former Barcelona youth player would not have played in the return match anyway because of suspension. Arsenal is also without Arshavin (calf), William Gallas (calf) and Alex Song was ruled out on Monday with a groin injury that puts further strain on the defense.

Wenger said Samir Nasri will lead the offense, while Theo Walcott could play a big part after starting the Gunners' rally last time with a goal.

Although Guardiola lauded Walcott's qualities, he didn't think the England winger would be the English team's salvation.

“Walcott was not the determining factor. The determining factor was (goalkeeper Manuel) Almunia who stopped a thousand shots,” Guardiola said. “If he hadn't made all of those saves we probably wouldn't be talking about things the way we are.” Almunia should expect more of the same from Guardiola's charges, especially with 35-year-old Sol Campbell or the inexperienced defender Craig Eastmond likely to fill-in in defense. Campbell is a doubt because of fatigue after playing 90 minutes against Wolves.

Barcelona may also have Andres Iniesta back in attack early from a leg injury, Guardiola said.

“We have to forget about the last performance against Arsenal. We have to play good again,” the Catalan coach said. “We're going to try to be ourselves and to get the ball and I think Mr. Wenger thinks the same. The team that has the ball more is going to win.” Ibrahimovic, who scored both goals at Arsenal, tore a muscle in his right calf, while Pique hurt his leg, although he was already suspended for the game.

Rafael Marquez and Gabriel Milito, who hasn't started a Champions League match in nearly two years, are the most likely fill-ins, although midfielder Yaya Toure could play despite hurting his ankle against Athletic.

“For any team to be without their two central defenders, the two players who play week-in, week-out, you know they are people they build the team around and it is not good for them - it is good for us,” Bendtner said.

Barcelona does have Lionel Messi back to his scoring ways after the winger netted for the first time in four games on Saturday for his league-leading 26th goal and 35th overall.

Guardiola may lean toward Bojan Krkic in place of Ibrahimovic instead of Thierry Henry. Henry received renewed criticism over his lackluster campaign following his performance in last week's draw at Emirates Stadium, while Krkic scored two goals against Athletic.

“It's a great game, a nice game to enjoy,” Krkic said.

“I'd like to play. We'll see, right?” Barcelona's season may be on the line this week. It plays at Real Madrid on Saturday in a match that could determine the Spanish league winner with both clubs even on points at the top of the standings.

Still, Arsenal's task is enormous - Barcelona has outscored opponents 13-2 at the Camp Nou in four knockout round games under Guardiola, whose team thrives on pressure games.

“After wining six titles the people demand more,” Guardiola said.