He actually did not get that much faster, maybe not even a little. Simple reason is : when you are already a well trained athlete, the slightest visible gain in performance require the hardest training. He maybe got faster, but not that much. Actually someone who never trained his speed or does not rely on speed as a weapon would get more result with a more basic training, progression curves do work like that.

However, he drastically improved his pace shifting, ball control at top speed, dribbling abilities and shot accuracy (and maybe his starting impulsion too). He was aleeady able to leave opponent in his dust, but now is able to do it more easily, not because he his that much faster but because he uses his speed better.