Even though the Bundesliga outfit trail 3-1 from their first-leg clash with the Catalans in Germany, the forward insists that they will not lack motivation at Camp Nou
The German outfit's hopes of reaching the quarter-finals appear slim at best, given that they go into the game in Catalunya trailing 3-1 from their first meeting at the BayArena.
However, while Kiessling admits that their qualification hopes appear remote, Leverkusen are determined to give a good account of themselves at Camp Nou.
"I do not know if we have a realistic chance [of going through]," the forward confessed. "But we want to trouble Barca."
Since losing at home to the reigning European champions, Leverkusen have racked up three successive wins in the Bundesliga, routing Augsburg, triumphing 2-0 at Koln and then upsetting Bayern Munich by the same scoreline on Saturday.
And Robin Dutt's men are brimming with confidence at the moment.
"First the derby win in Koln, now at last a victory over Bayern," Kiessling exclaimed. "It was really fun to celebrate with the fans [at the weekend]."
Kiessling's fellow forward Eren Derdiyok claims that Leverkusen have taken great confidence out of their three-game winning streak and that they are keen to prove against Barcelona "that Bayer can handle playing in the last 16".
The Switzerland international also revealed that with Leverkusen now having climbed to fifth in the standings, they are now eyeing Schalke in fourth place.
"At first it seemed we would not even be in the Europa League, but now we can even dream of reaching the Champions League," he enthused in response to a question from Goal.com. "This must be the goal."
After the midweek trip to Camp Nou, Leverkusen return to Bundesliga action away to Wolfsburg on Saturday.
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