personally i would get:
Bogdan Shust- Shaktar Donetsk GK
Joleon Lescott- Everton CB
or
Dmytro Chygrynskiy- Shaktar Donetsk CB and
Samir Nasri- Marseille CAM
or
Daniel Carvalho- CSKA Moscow CAM
and to the previous post about vidal, he plays for leverkusen and is worth £5.5m but i think hes more suited to left full back than CB, however he can still play there to a top class level.
Claudio Rodriguez is also a LB really
and if your considering Argentinian players, i would suggest Belluschi (AM), Alayes (CB) and Villar (GK), but i dont think these are good enough for the first team of lyon really, though very good squad players