Why?
10 million is a lot. He only costs that much because he has so many seasons in the Premier League, but frankly, he's been getting very slow the last years.

There was a time when he was fast, but right now he's pretty much the same age and same quality with Alex Song (who was also very fast and even better than Kouyate in the same period) and who is now a free agent and can be snapped up without paying anything.

Or Onazi from Trabzonspo, a younger player, who would cost only 2-3 million.

This only taking into consideration similar African players, but there are a number of quality defensive midfielders available for free or for small fees, like Collback or Henriksen from Hull, who's in his last year of contract.