The Danish champions are the runaway leaders in their domestic league, and top Group D with two wins from two, while an inconsistent Barca lie second with four points after a 1-1 draw away to Rubin Kazan.
Although Barca stormed back to beat Valencia 2-1 at home in La Liga on Saturday, they have struggled to find the back of the net in matches at the Nou Camp and a 2-0 defeat to promoted Hercules and a 1-1 draw with Real Mallorca there have raised eyebrows.
New signing, Spain striker David Villa, has played a total of eight games and scored four goals but he has been guilty of some bad misses as Barca have failed to convert their overwhelming domination of possession into goals.
"It's all a question of runs of form, and when my luck changes we'll get the goals for Barcelona," Villa told sports daily AS on Monday.
Xavi pulled out of Spain's recent Euro 2012 qualifiers to recover from pain in his Achilles tendons, and returned on Saturday when he set up both goals for midfielder Andres Iniesta and defender Carles Puyol.
After the game though, in which he was substituted late on, Xavi admitted he was still suffering discomfort and Guardiola said he was not yet ready to play a game every three days.
MASCHERANO CHANCE
Xavi trained apart on Monday, and could sit out Wednesday's game which may give Argentina's Javier Mascherano a chance for a rare start.
"Xavi is a very important player for this team, for the way that he plays," Mascherano told a reporters on Monday. "I have not come to play because someone is injured. What I want is to help the team when the coach asks."
Copenhagen warmed up for Wednesday's match with a 5-0 demolition of OB Odense in the Danish league on Sunday, with a hat-trick from Cesar Santin.
They top the standings, 12 points clear of second-placed Midtjylland and have won both their Champions League matches against Rubin Kazan and Panathinaikos without conceding a goal.
Coach Stale Solbakken was not about to let the success go to their heads.
"It may well be that on Wednesday it is us - just like OB now - that sit in the losers' dressing room having been taught a lesson by a team that is much, much better," Solbakken was quoted as saying by daily newspaper Politiken.
Former Chelsea winger Jesper Gronkjaer, who is sure to be in the starting line-up on Wednesday, said: "We must face it that Barcelona are several levels above us."
Santin was not expected to be in the starting line-up despite his hat-trick on Sunday.
Probable teams:
Barcelona: 1-Victor Valdes; 2-Daniel Alves, 3-Gerard Pique, 5-Carles Puyol, 22-Eric Abidal; 14-Javier Macherano, 16-Sergio Busquets, 8-Andres iniesta; 17-Pedro, 10-Lionel Messi, 7-David Villa
Copenhagen: 21-Johan Wiland; 2-Zdenek Pospech, 15-Mikael Antonsson, 17-Oscar Wendt, 25-Mathias Zanka; 6-Claudemir, 8-William Kvist, 20-Martin Vingaard, 30-Christian Bolanos; 14-Dame N'Doye, 10-Jesper Gronkjaer
