i don't believe we need to sign any defender other than a right back - hopefully naughton, if not, who knows. there aren't a huge amount of right backs to choose from! russell martin has done much better in his usual position since christmas after a shaky start so i'm not against him staying there. i literally cannot think of any centre backs i'd rather have at the moment who wouldn't cost £8m+. and thats the problem isn't it - plus, the two young kids ayala and bennett both have enormous potential - go with them, assuming they remain injury free and keep ward and whitbread as back up. i would believe, if tierney is fit and we could get naughton, that is a top half premier league defence.
Russell Martin is handy to keep as utility player in case we really are troubled by injuries. Our back up though has turned more or less into our main defence this season.