It's not a surprise to me, because this is not the first time Sassuolo get a winning results that were beyond predictions when meeting a top team. I personally think that Sassuolo is "the big four killer", and the club that often gets surprises is AC Milan, and its happens from few season back. However, this is an advantage for AC Milan, because currently Milan has the same points as Inter Milan. There is little hope for Milan to be able to provide pressure to Inter Milan.