But even though they have received around £50m in transfer fees this summer for Ricardo Carvalho, Paulo Ferreira and Deco, they are over-stocked in midfield and would consider a significant bid.
Maniche is a more attackminded player than Vieira and his goal in Portugal's semi-final against Holland was voted the best in the tournament. He is a UEFA Cup and European Cup winner at club level.
He started his career at Benfica and spent three seasons on loan at Alverca before moving to Porto two years ago and making his name under Jose Mourinho.
If that move stalls, Arsenal may consider going for Spanish international Baraja, who has been impressive for Valencia on the three occasions they have faced Arsenal in the Champions League in recent years.
He cost Valencia £8m from Atletico Madrid four years ago and if Arsenal match that figure, the Spanish champions, who are still massively in debt, would be likely to sell him.
Vieira's motivation for leaving is also about proving himself in Spain. He has twice turned down the chance to go to Real in the last four years and he knows that at 28 there is little prospect they would come back in again.
The Frenchman, who has been at Arsenal for eight years following his move from AC Milan, has not officially asked for a move but has let both Wenger and vice-chairman David Dein know that if a fee - and his personal terms - can be agreed he wants to go. In his time at Arsenal he has won three Premiership medals and is hoping that the club will take his contribution into account and not force him to put a request in writing.
For Wenger, the future post-Vieira would involve persuading his other top stars, such as Thierry Henry, that the team could move forward without their skipper.
Meanwhile, Arsenal gave new signings Robin van Persie and Mathieu Flamini a final run-out before Sunday's FA Community Shield against Manchester United in a 0-0 draw with Beveren last night. Lauren and Jermaine Pennant also played.
The game gave the Gunners another chance to run the rule over Beveren's Ivory Coast pair Marco Ne and Emmanuel Eboue, who have been training with the Londoners but played for the Belgian side.
The collaboration between the two clubs was further demonstrated when Christian Swegler began the game for Arsenal but swapped sides at half-time.
