He's said as much. Just after his win over Novak, he mentioned to a reporter that he still struggles to "get up" for the regular tour matches that don't have the big names. Also, he hasn't had a coach for well over a year now.
I mentioned early about Sam Querrey's capabilities so, even though, of all the people I would've put in the final, Sam wouldn't have been at the top of that list, I know that he has the ability to eke out big wins, especially if his more talented opponent is flat.
I didn't even bother with Nadal and Cilic and I fell asleep during the Kyrgios and Querrey match. I mentioned like, last year that 90% of Sam's matches put me to sleep, no matter who he plays. His matches against Isner have been the worst though.