Thiem has progressively declined every year once Summer hard courts have started.
2018 has started with what appears to be a nice drubbing of Donskoy. Thiem:
1. won 91% of first serves which is phenomenal and looks more at ease with the pace on first serve game trading a touch of pace for better placement
2. won 36% of first return points in the match (right on track and a strength of his game on hard courts.)
3. won 56% of 2nd return points; again dandy
....
....
4. Did all of the above, but only won 44% of 2nd serve points and failed once again to serve out first set from 5-3.

Thiem's hard court malady may be worsening.

Again early 2017 and all of 2016 he was 53-54% on 2nd serve return won on hard courts, but then sunk to around 48% for the 2nd half of the year.
I love stats and never really seen anything like Thiem's 2nd serve points won drop which has dropped off a cliff on hard courts. Crazy, crazy stuff when all of his other stats have improved quite nicely. My best guess is purely mental/strategy, but would have no idea what to tell Thiem to do about it. Maybe this is not mental and has to do with his kicker serve going down the drain pure and simple; if this is the case then he's got to focus on his 2nd serving. (Boris Becker is still available.

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