Bayer Leverkusen captain Lars Bender says holders Barcelona still present his side with a huge challenge away in Tuesday's Champions League group match -- even without injured star Lionel Messi.

The Barcelona playmaker is expected to miss up to eight weeks with a knee injury, but Leverkusen face a daunting task despite beating Werder Bremen 3-0 away on Saturday to climb to fifth in the German league.

Messi's injury has little impact to Leverkusen's status as underdogs at the Camp Nou.

"Barcelona have enough top players in the squad and the game remains a huge challenge," said Bender.

The Germany midfielder says his side must show some courage in Barcelona having been mauled 7-1 on their previous visit in 2012, when Messi bagged five goals.

"We're found our way back on track, but now we have to attempt to be more courageous," said Bender, who has shaken off a knee injury.

Goals by Swiss forward Admir Mehmedi, winger Kevin Kampl and Germany Under-21 talent Julian Brandt sealed Leverkusen's win in Bremen.

"Every footballer dreams of playing in matches like this, we all know how strong the opponent will be, but we want to bring our own game to their pitch," said Kampl, who scored his first league goal since his transfer from Borussia Dortmund."

Leverkusen coach Roger Schmidt was delighted with Bender's performance alongside fellow Germany international Christoph Kramer in the defensive midfield.

"I was especially pleased that we gave the opposition hardly any chances and it is important for us that Lars Bender is fit," said Schmidt.

At least Messi's injury guarantees there will be no repeat of the embarrassing shirt-swapping affair of 2012.

When Barcelona beat Leverkusen 3-1 in their last 16, first-leg win three years ago, Bayer defender Michal Kadlec asked Messi for his shirt at half-time, but a row broke out when teammate Manuel Friedrich, who was marking Messi, claimed it for himself in the break.

Kadlec, who scored the Germans' only goal, eventually got another shirt off Messi at full time, but Leverkusen sporting director Rudi Voller made the pair auction the shirts for charity after getting wind of what had happened.