If decent players are actually available then yeah maybe we should buy. But we don't need lots and we have a lot of defenders its just a shame most of them are injured. So I wouldn't panic buy a Defender. Maybe bring one in on loan, But an experienced defender like Albiol or just someone who isn't really getting a game at their club.
As for decent players I still think youthful players are the way to go.
Rodwell
Martinez
ATTACKING
Erickson
Gotze
Lucas
Ganso
Shaquiri
Thiago
Modric would be my preffered choice. And I really don't want us to spend big on Sneidjer. I would rather take the risk on the youngsters unless they offer him for 20 MIL.
Alba or Cristico would probably be good options for LB as well. But Fryers looks like he will be able to push Evra.