Sure, but he pulled it out, and when players make a comeback it doesn't all happen at once. What can I say? I don't watch him as closely as some other players, but the guys I have liked over the years have all had bad periods.
Serve, of course, is absolutely crucial. But what has been most shocking to me this year has been the fall in his return game. I have him as the greatest returner on HCs over the last 25 years, with Murray and Agassi being very close, absolutely amazing.
This is a guy who has won around 33% of his return games on HCs for his career, and for this era that is beyond belief. It means that when he was on top you could expect him to break about 1 out of 3 games.
This year, so far, it has dropped to around 26%, which is a HUGE drop.
Something like that happened to Rafa too when he hit his worst slump, but for him the worst was the service game. No so much of a drop in return stats.
When I go here:
http://www.atpworldtour.com/en/stats/return-games-won/2017/hard/all/
And see Novak at around 21st place, that's a shock...