Sir Alex feels Rafael and Fabio will shake off the injury niggles that continue to hinder their progress at Old Trafford.
The da Silva twins have confirmed their huge potential since arriving in a double deal from Fluminense but have struggled to stay fit enough to hold down a regular place.
Injury problems have caused the South Americans to finish games early and both limped out of the Carling Cup defeat to Crystal Palace recently. Although Rafael is back in training, his twin remains sidelined and it is an issue that the manager acknowledges.
However, Sir Alex has faith in the exciting duo and admits he loves their swashbuckling style, even if it does cause them to pick up knocks along the way.
"The two of them are terrific talents," declared the boss. "But they keep getting injuries, the kids are always getting them.
"I'm hoping that maturity eradicates all these things they have but it's all different types of injuries you know.
"They're so sturdy. They're strong boys but, possibly, they're a wee bit optimistic in terms of the challenges they make. They always put a foot in, in terms of attacking-wise, and are always getting injured going into attacking moves.
"The boys just don't see danger. Bryan Robson was that way too, 'Bang, on they go'. They're only 21, you know, they're young," he stressed. "You forget they were in the team as teenagers.
"I think both of them could play right-back [in the long-term]," stated Sir Alex. "There's nothing between the two of them really. They are both excellent talents and really positive players. It's what I love about them. They don't have an inkling of fear in the way they play at all.
"They've always been really positive lads and it's the Brazilian nature."
