The Blues head into the fixture with a 1-0 advantage, and while Wenger criticised Chelsea's tactics for the goalless draw at the Emirates on Saturday, the Frenchman believes that the Spanish giants are slipping.
"We have seen at Chelsea last Wednesday night that this is not the Barcelona of last year," the Express quotes Wenger as saying.
"At the moment [Lionel] Messi looks a bit tired. He is still dangerous, even tired. But he is not as sharp as he was before and if Chelsea defend like they did the other night they have a chance."
If Chelsea end victorious tomorrow night, Roberto Di Matteo's side will either face Bayern Munich or Real Madrid in the final at the Allianz Arena in Germany.