Lyon, who won 3-1 at home last week after an exciting first leg of the all-French quarter-final clash, have greater experience of European battles and boosted their morale by winning 2-1 at Stade Rennes on Saturday to go top in Ligue 1.
Bordeaux, by contrast, have just lost three matches in three different competitions, the latest a 2-1 home league defeat by Nancy at the weekend to drop to fourth in Ligue 1, albeit just one point off top spot.
A few months ago, when the French champions looked the most solid side in the country by a long way, many would have predicted they could overcome a 3-1 first-leg deficit to bounce back before their fans.
The picture has changed, however, Bordeaux having fallen 3-1 to Olympique Marseille in the French League Cup final before losing at Lyon by the same score in Europe and then stumbling against Nancy in domestic action.
Once their main strength, their defence has looked shaky and porous in all those outings and there is a clear question mark over their ability to handle the pressure of big matches.
"Our defence, which is what makes the difference at the highest level, is mediocre at the moment and that affects the whole team's confidence," Girondins Bordeaux coach Laurent Blanc told reporters.
DIARRA BACK
"It's in difficult periods like this one that you see what individuals and teams are made of," Blanc added.
"If we have character, we will show it on the pitch, starting from Wednesday's Champions League match, but I don't feel too many positive signals before that game."
Good news for Blanc is that holding midfielder and captain Alou Diarra, who missed the first leg through suspension, will be back and might make his defence more stable.
The mood is very different in the Lyon camp, where morale is high after a convincing win at Rennes despite the fact that coach Claude Puel had rested a handful of first-choice players.
"We don't have a team, we have a group," Puel, who will miss Argentine striker Lisandro Lopez and fellow forward Sidney Govou through suspension to face Bordeaux, told reporters.
"We're in the last straight, with every game a final, and we need more than 11 players for that."
What is at stake for Lyon, who won seven Ligue 1 titles in a row before losing their crown to Bordeaux last year, is not so much to prove that they remain the top side in France.
What they really want is to make an impact in Europe at last by reaching the last four of its premier club event for the first time to set up a clash with Manchester United or Bayern Munich.
"We qualified for the Champions League for the last 10 years and this is our fourth quarter-final," Lyon president Jean-Michel Aulas told reporters. "Everybody at the club desperately wants to move a step further."
Probable teams:
Girondins Bordeaux - 1-Cedric Carrasso; 21-Matthieu Chalme, 25-Ludovic Sane, 2-Michael Ciani, 28-Benoit T
