Some coach needs to convince him to play more aggressively and he can win Slams. He has solved his serve toss to a large extent by tossing lower and so his serve seems more reliable under pressure. He is too content waiting for errors rather than imposing the point patterns he wants. He should hit his FH DTL more to get more rallies on the BH wing early, he should go for more on his BH to hit more winners, he should hit closer to the sidelines, he should hit inside-FHs more, he should take a more aggressive court position etc. He should try to play more like Djokovic.