"Everyone knows that his serve and forehand are his main weapons, but he absolutely needs to improve his backhand if he wants to rise to a higher level," Sock explained. "If his backhand also ...

As Rinderknech was doing the same with a 40-0 lead in the second game, a second serve to the body forced Fritz to hit a two-handed forehand.

American Jack Sock battled back from a set down to beat qualifier Filip Krajinovic 5-7, 6-4, 6-1 and win the Paris Masters title on Sunday, snatching a place at the World Tour Finals.

Yet when Sinner reaches the point just before he swings his arm to hit the forehand, his racket is pointing in what appears to be a position that will make it hard to get a clean connection.

Rinderknech finally broke the run to get within 5-6 and was back on serve but on the next rally Goldhoff hit a forehand that just stayed in near the baseline and Rinderknech was long with a forehand.