It worked in the Premier League on Sunday, when United boss Alex Ferguson was on hand to see Fabregas score both Arsenal goals in a 2-0 win over Middlesbrough.
"It could be that we will do it again because it was quite convincing," Wenger said in a newsletter to fans before the first European meeting between the two English clubs whose rivalry dates back 115 years.
"At the moment you are encouraged to be very cautious at home but very audacious away from home" Wenger said on the Arsenal website (www.arsenal.com).
"We will go there with belief," Wenger told reporters after the Boro match. "We will go there like we do everywhere in Europe to try to score and win."
United, who beat Chelsea in last season's all-English final in Moscow, are bidding to become the first club in the Champions League era to retain the European Cup.
Saturday's comeback against Tottenham Hotspur, when they scored five goals in 22 minutes to turn a 2-0 half-time deficit into a 5-2 victory, showed them at their most potent.
Giggs, named the Professional Footballers' Association Player of the Year on Sunday, said: "They don't come much bigger than a Champions League semi-final at Old Trafford and I am looking forward to it but I am more interested in beating Arsenal rather than the 800th appearance."
Arsenal's former United centre-back Mikael Silvestre has a back problem but Emmanuel Adebayor and Abou Diaby should be fit.
Manchester United: 1-Edwin van der Sar; 22-John O'Shea, 5-Rio Ferdinand, 15-Nemanja Vidic, 3-Patrice Evra; 8-Anderson, 16-Michael Carrick, 11-Ryan Giggs; 7-Cristiano Ronaldo, 9-Dimitar Berbatov,
