Honestly, Kyrgios sold this notion that he only gets motivated against the big guys and suddenly it became set in stone. I don't buy this just one bit. He is a big server, and that's exactly what happens with big servers: one day they lose in the first or the second round, the other they take out or at least scare a big name. Kyrgios is bit more than just a big server, as his movement is better, but say whatever you wanna say, his stats are basically the stats of... a big server. He does not break serve significantly more than an Isner or an Anderson (in fact, probably less). If he gets beaten by Querrey or some other guy it is just because the other guy played better.
Nothing against Kyrgios -- in fact I am starting to really like the guy -- but I can't help but feel that people see whatever they wanna see in the guy.