Barcelona travel to Germany smarting from only their second La Liga defeat of the campaign after they crashed to a 3-2 reverse at Osasuna on Saturday that left them 10 points behind leaders Real Madrid.
The Spanish, European, and world champions initially seemed to suffer from the sub-zero temperatures in Pamplona and some uncharacteristic defensive lapses left them two goals down at half-time in a domestic league match for the first time since Pep Guardiola took over as coach in 2008.
They managed to lift their game for the second half and Guardiola, who rested Spain midfielders Xavi and Andres Iniesta and introduced their international team-mate Cesc Fabregas only in the second half, said he wanted more of the same on Tuesday.
"We are travelling to Europe to defend our title as champions," Guardiola told a news conference.
"Our performance in the second half was the path we need to follow to defend a Champions League," the former Barca and Spain midfielder added.
Sergio Busquets missed out in Pamplona after sustaining a deep gash to his leg the previous weekend and if he does not return in time his holding midfield role will likely be taken by Javier Mascherano.
"It was a painful defeat," said Iniesta of the Osasuna result. "We reacted in the second half but it wasn't enough and now we have to see things through to the end and prepare for the Champions League game."
Leverkusen, who lost to champions Borussia Dortmund 1-0 in the Bundesliga on Saturday, will be missing their most experienced player, Michael Ballack, after he pulled a muscle during training on Sunday.
The 35-year-old was not certain he would start anyway after having been reduced to a substitute in the last few games, with club boss Wolfgang Holzhaeuser saying the former German captain had failed to deliver since joining in 2010.
Ballack is set to leave at the end of the season and his absence on Tuesday could prove crucial for his club.
Coach Robin Dutt will have defender Michal Kadlec back after his league suspension and is hoping the team's desire to do well in the top European competition was strong.
Right-back Danny da Costa also looks also fit to play after injuring himself in training on Sunday following a clash with a team-mate.
"Confidence is there, on how the team works. There is passion," said Dutt, whose team - last season's runners-up - are sixth in the league 15 points off the top.
"But for that last touch everyone needs to work harder. We need to work harder up front, all of us. We won't have many chances against them," Dutt said.
Defender Daniel Schwaab said: "It is a highlight for us to be playing the best team in the world. Some top players were rested at the weekend but I assume they will all be back against us as they throw all their weight into this competition."
Bayer Leverkusen: 23-Bernd Leno; 14
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