The Zenit midfielder believes the German side is weaker than last season’s Champions League runner-up squad after a poor start to the Bundesliga campaign.
Jurgen Klopp reached the Wembley final of the 2012-13 edition of the competition and topped a tricky group containing Arsenal and Napoli this time out.
BVB was drawn against Luciano Spalletti's men in the last 16 and Tymoshchuk, who was part of the Bayern Munich team that beat Dortmund in London, believes the German giants have declined since May.
“Borussia are third in the Bundesliga. In my opinion they are not in the best form right now,” Tymoshchuk told reporters. “They collected points against other leaders of the league and in the Champions League, but it's not the same team that reached the final last season. They were much stronger at that time."
Zenit, which qualified in its group behind Atletico Madrid, will host the first leg Feb. 25, before travelling to Signal Iduna Park on March 19.