It's an interesting argument, as a CB in a 2, he's generally quite good, because he is disciplined in that role to defend, but he's poor in a 3 CB system, because he remembers being a LB, and plays like an attacking LB, and he's awful at LB because he's asked to attack, which he does, but he forgets defending altogether.
Clichy on the other hand defends as a LB, but because he's asked to attack he does, but has no real idea how, as a CB in a 3 he's not got the reliability, and gets caught between the 2 roles, but as CB in a 2 looks OK, but not great.
We've a similar dilemma on the right. Sagna is the better defender, but Zab is the better attacker, Zab can also play the tucked in role quite well, as he understands the DM role quite well, whilst Sagna can play well as a a CB in a 3, but I don't think Zab could.
If we could somehow combine the abilities of both FB's, on both sides, into 1 single player on each side, they'd probably produce the perfect player.
It will be interesting to see how Pep deals with this in the summer, especially given the relevant ages of all 4, I don't think we will replace them all, I think we'll keep 2, so my bet would be Zab and Kolarov for their attacking abilities.