Hosts Sparta started their league campaign in impression fashion by taking 16 points from their opening six games, but since then they have lost four successive matches in all competitions- their worst run since 2005 - with their latest defeat being a 1-0 reverse at arch rivals Slavia Prague on Saturday.
That derby loss was a huge blow, but Sparta coach Vitezslav Lavicka insists the mood in the camp is now back on the up.
"We try to stay positive and I have a positive impression of the dressing room. There was disappointment after Saturday's failure over the weekend and on Monday, but on Tuesday there was already an improvement in the mood and the desire to give it everything on Thursday. The team certainly don't feel any scepticism," he said on his club's website.
Despite Sparta's poor run, which included a 2-1 defeat to Lyon in their opening Group I match, Lavicka is adamant his side will not look to go on the defensive against last season's Europa League runners-up Athletic.
He said: "Our motto is to go for victory in every game. We do not play a passive role and wait.
"We know that we are not the favourites in the group, but our intention and goal has not changed."
Athletic are not in the best form either heading to the Czech Republic following a hugely disappointing start to their campaign.
Much was expected of the Basque side following their superb success of last term, where they reached the finals of both the Europa League and the Copa del Rey, but they have only won three of their 11 competitive games so far this season.
Athletic are also without a win in four games and, like Sparta, they too suffered derby disappointment at the weekend after slumping to a 2-0 loss at Real Sociedad - a result that left Marcelo Bielsa's men in the bottom three of La Liga.
Striker Ibai Gomez said in the wake of that loss: "We've played better and worse games and what we need to do is correct the mistakes. I'm convinced that we're going to get through this like last season.
"The positive is that this week we have two very important and nice games - against Sparta Prague in Europe and Osasuna in the league - and we need to change the dynamic as soon as possible."