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.
"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.
"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."
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.
"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."
