Re: Nishikori will win a slam
If Kei can develop his serve into even a semi weapon, he will very tough to beat for anyone, including the top 4. His game is amazing otherwise, brilliant ROS and can bully even some of the biggest hitters on tour off the ground - it was incredible how he put Berdych constantly on the defensive in their QF match here in Tokyo. If he remains injury free and beefs up his serve, a Slam is a more than realistic expectation.
A good indication of how good he already is is his H2H against the players currently ranked 5-8:
2-1 vs Ferrer (1-0 in Slams, 1-0 Olympics)
2-0 vs Tsonga (1-0 in Slams)
3-1 vs Berdych
He is completely owned by Del Potro: 0-4, Delpo won all 10 sets they played in mostly easy fashion, but JMDP is on another level and a horrible matchup for him anyway. Against the other 5-8 guys, he has done pretty well - and also let's not forget that he has already beaten Nole once. Even without further improvement on his serve, reaching the top 8 would be a very realistic immediate goal.