You are looking at it the wrong way. Sterling's performance was on a consistent level from the beginning of the season. Sane just recently notched up most of those stats. And WC and international matches have everything to do with it. Netherlands are in the semi of new international cup by beating two very good teams. Yes sterling didn't do much and in that theory Sane literally sat at home.
And what's with the argument with Mane? Just coz Sane has better stats for 4-6 months he should surpass or be equal to it?
City and LFC were excellent reviews according to me. Koulibaly and VVD are the best defenders at present and the rating shows.