Viktor Troicki is a player with a big game who can beat pretty much anyone, but lacks the consistency to do it on a regular basis. He endorses the Babolat Pure Aero Plus, but is actually an older model of the Babolat Pure Aero VS strung with a hybrid of Babolat RPM Blast and Babolat VS Touch.
Anyone who has tried some iteration of the Babolat Aero Storm, which is the older name for the Pure Aero VS line (Jack Sock is another user of this line of racquets), knows it is a very control-oriented frame with a pretty high stiffness rating and thus requires a softer string setup. Either you string it low like Sock does (below 40 lbs) or you have a hybrid string setup such as Troicki.
Here is a close-up of Troicki’s racquet after he smashed it to the ground in yesterday’s loss to Milos Raonic in Miami Open (Masters).