From The Secret Footballer:

I spoke to a scout at Chelsea and he told me that watched Tiote for an entire season and drawn the conclusion that, for a defensive midfielder, it was alarming how often he was caught on the wrong side of the opponents deep-lying striker or advanced midfielder and as a result, very often ended up fouling the player in his attempt to get goal side.

Although to be fair that was to make a point about how many managers felt black players could not be relied upon to be centre midfielders and were better suited to wide attacking positions.