Sergio Aguero has a proven scoring record against Barcelona and the Manchester City forward may have a crucial role to play if his side is to upset the odds and reach the Champions League quarterfinals for the first time.

City trails 2-0 ahead of Wednesday's last-16, second leg at the Nou Camp, a Lionel Messi penalty and a late Daniel Alves goal in Manchester last month put the Spanish champion on the brink of its seventh consecutive appearance in the last eight of Europe's elite club competition.

Aguero, who missed the first leg through injury but returned for City's English League Cup final victory on March 2, scored five goals in 10 La Liga games against Barca for Atletico Madrid between 2006 and 2011.

They included a dramatic winner, his second of the match, in a 4-3 success at the Calderon in the 2008-09 season that prompted the kind of wild celebrations he unleashed with the goal that sealed the Premier League title for City in 2012.

The player, known as 'Kun' after a Japanese cartoon character, also netted a double in the same La Liga fixture a year earlier, a 4-2 win for Atletico.

He has never tasted victory at the Nou Camp though in six visits but did score in a 1-1 draw in 2006-07.

"As always in important games the individual performance of players is key," City coach Manuel Pellegrini, who has labeled Aguero the third best player in the world behind his Argentina teammate Messi and Portugal forward Cristiano Ronaldo, said on the club's website on Monday.

"Of course it is difficult," said the Chilean in his first season in charge following stints with Villarreal, Real Madrid and Malaga.

"But I don't have any doubt that we are going to Barcelona thinking that we can do it, that we can beat them in Camp Nou and we will try to have our revenge there."

Pellegrini also has experience of Barca's daunting arena, Europe's biggest stadium. He faced the side 22 times during his La Liga coaching career but only managed four victories, most recently a 2-1 win for Villarreal at the Nou Camp in March 2008.

He lost both Clasicos against Barca as Real coach in the 2009-10 season, 1-0 away and 2-0 at home.

"It is difficult because they are a very good team with great players and that is the most important thing," Pellegrini said.

Pellegrini's players will take heart from a fine performance in Germany in their last European away game when the team came from two goals down to beat Group D rival and defending champion Bayern Munich 3-2 with both sides already through to the last 16.

History is against City, however.

Only twice in the Champions League has a team recovered from a first-leg defeat at home to go through, Ajax Amsterdam achieving the feat in 1995-96 and Inter Milan in 2010-11.