Left back.....

Koscielney - He's a little tto lightweight to play alongside Vermaelen in the middle, he's great on the ball though I think he would be excellent at LB.
 
Vermaelen is a left back. When we signed him as a CB the reaction in Belgium and Holland was shock, followed by laughter.
His goals overshadowed his defensive deficiencies in his first season, and his injury enhanced his reputation in his second season.
TV is over-rated as a CB (although he is the best we have)

And may i ask where you proof of this is??

Because at Ajax he played as a CB alongside Johnny Heitinga and when Heitinga left and joined Atlético Madrid in 2008 TV then played at CB with Jan Vertonghen for the next season before joining arsenal...

Do some research mate...
 
Oleguer and Vertonghen played most of Vermaelens last season as the CBs, with TV at left back.
Toby Alderweireld and Gregory van der Wiel also played at CB in games wherein TV was at LB.
 
Baines is the best option although i dont see Moyes letting him go for anything under £10 million, so the cheaper option is Jose Enrique and Gibbs is nowhere near good enough, yet