I think Mellberg was signed in view of playing Centre back... and Mellberg has already publically stated he's eyeing a the Centre Back positions at juventus.. It is part of the reason why he is leaving A.villa... He is not a natural Right back...
As far as i kno sagnol didn't play much this season... Lahm played RB and Lell played LB for a majority. This was considered their strongest line-up.
Lell - 32 starts
Lahm - 26 Starts
Sagnol - 9 starts