Not huge if we can't fit him into midfield because all our other weaknesses are prohibiting us from doing so, yeh ok he can play CB or wing back or whatever but he's exploited there due to his lack of pace. I think Carrick and Blind in the same team just won't work.
If it's true LVG doesn't think Herrera is strong enough for PL then we need Strootman A.S.A.P this window and FB/CB so we can get out of using these crappy 3 at the back formations.
Shaw and Rafael constantly pick up injuries as do our current CB's, who just aren't good enough anyway.
These are problems that could have been solved in the summer and if we don't strengthen in January then miss out on top 4 you can hardly say we don't deserve it when we have relied on a squad with 2 fullbacks and the muppets in defence like Evans to be a key part of the foundation in our team when losing all the quality/leadership/experience we had last summer.
Blind's lack of pace was never exploited because of his positioning. Also in midfield you don't need pace, it's an added bonus but not as important as for wingers and strikers. His intelligence is superb.