Da Silva lining at Old Trafford which can spell double trouble for rivals

Arsenal were undone in the FA Cup yesterday by the identical Brazilian twins Sir Alex Ferguson still struggles to tell apart.

And the irony is, if Arsene Wenger had had his way, Fabio and Rafael Da Silva might have been tormenting Manchester United rather than boosting their bid for the Treble.

For Fabio, who scored United's opener, has revealed: 'Arsenal were interested, but we chose United because they worked very hard and everyone knows them.

'And Senhor Alex (Ferguson) has always been very supportive of us. He likes to know what people are like, both on and off the field.'

That knowledge does not yet extend to being able to identify instantly who is who.

It used to be easier: shortly after they arrived as 18-year-olds in July 2008 Fabio was wearing a wedding ring after marrying his childhood sweetheart Barbara. But since then, Rafael has married and his wedding ring means the identity crisis has started again.

The United fans have even made a joke about the confusion. Adapting the Viva Ronaldo chant, they now sing: 'Running up the pitch, can't tell which is which, Viva Da Silva.'

The boys, from Petropolis, near Rio de Janeiro, were spotted by United as 15-year-olds playing for Fluminense in Hong Kong. Rafael was right-back, Fabio on the left.

Both were soon starring for the Brazil Under-17s - Fabio was captain - and although they were tied to United, they were not allowed to move to England, with their parents, until their 18th birthdays. Soon after their arrival each made his first-team debut.

Rafael has now made 66 senior appearances, is close to establishing himself as first-choice right-back and has been called up by the full Brazil squad.

Chances for Fabio, who has played 27 times for the United top team, have been limited with Patrice Evra first-choice left-back.

Which is why opportunity may beckon in an attacking role - provided Sir Alex knows who is who.

Ferguson is not the only one who has struggled to tell them apart.

During a Carling Cup tie at Barnsley in 2009, referee Chris Foy - ironically, yesterday's match official - booked the wrong Da Silva, Fabio.

United appealed, and the yellow card was rescinded.

The reason? Mistaken identity!