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.
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. 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.
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.
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.”
In another Wednesday clash, Manchester United, minus Wayne Rooney, take on Bursaspor at Old Trafford. Rooney, who according to coach Alex Ferguson has expressed a desire to leave United, is nursing an ankle injury.
If United get back to winning ways against Bursaspor, they move to seven points and into a strong position to advance from Group C. Ferguson, though, will be wary of another upset against Turkish opposition.
United lost at home to Besiktas last season in their first home European defeat for four years, although by then they had qualified for the knockout stages of the 2009-10 competition.