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.
Wenger said the rule that makes away goals count double in the event of a tie made an adventurous approach essential.
"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).
There is a world of difference between beating relegation-threatened Middlesbrough at home and facing the European champions at Old Trafford, where United will look to extend their record unbeaten Champions League run to 24 matches.
"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."
The prize is a place in the final in Rome against Barcelona or Chelsea, who meet at the Nou Camp on Tuesday.
POTENT DISPLAY
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.
Notwithstanding their penalty shootout loss to Everton in the FA Cup semi-final last week, United have recovered from their recent blip when they lost to Liverpool and Fulham in successive games and are now unbeaten in their last seven matches in regular or extra-time.
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.
The result was achieved without Ryan Giggs, who could return on Wednesday for his 800th appearance for the club -- 10 years after his famous goal against Arsenal in an FA Cup semi-final replay put Manchester United on course for the treble in 1999.
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."
United will be without injured club skipper Gary Neville.
Arsenal's former United centre-back Mikael Silvestre has a back problem but Emmanuel Adebayor and Abou Diaby should be fit.
Possible teams:
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,
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