It's not really an upset that Isner beat Chung in straight sets today 6-1 6-4 as Isner is seeded higher, but based on form coming into this match, I would have put money on Chung winning today. Of course, I also picked Kyrgios to take out Zverev last night, so what do I know?
Of course, when he's in god servebot mode, he's tough to beat.
https://twitter.com/user/status/979092832047673344