Jack Sock: Sock started off the year better than he could have hoped, but since the clay season started his results have been worse than anyone could have predicted. He lost in the first round at the US Open, Cincinnati, and French Open, and second round in Montreal and Wimbledon. This was supposed be the year Sock took a big step forward, as he’s well-adjusted to life on tour and he seemed to be coming into his own. Instead, he’s taken a surprising step back, and is about to get passed by the younger generation of Americans if he doesn’t turn it around soon. It’s possible the rest of the tour has simply figured out how to play Sock and take full advantage of his backhand, which he has to go to great lengths to avoid being exposed. But despite all his struggles, the talent and athleticism remain. Sock is more than capable of posting some good results anytime he sets foot on a quick hard court, and he needs them about as much as anyone on tour.
Dominic Thiem: Thiem may have cemented himself as a fixture in the top ten, but it’s time he make some noise on surfaces other than clay. He’s got an explosive game that can translate well to all surfaces, but it’s well known that he likes the extra time clay gives him for his long strokes to develop. If he can have a few big results on the quicker surfaces common during the Asia and European swing this fall, his confidence should be high heading into next year. His loss to Del Potro in the US Open after having a two-set lead and match points was as devastating as it gets, and a strong fall season would help Thiem put it behind him. His fall didn’t start out well, losing to Guido Pella in the second round of a 250 in Chengdu, China. But if there’s one thing we know about Thiem it’s that he’ll enter more tournaments than anyone else on tour, meaning another opportunity is rarely more than a week away.
Grigor Dimitrov: Dimitrov is the master at disappointing when faced with big expectations, but stepping up just when you’re ready to give up on him for good. After his strong start to the year, including his run to the semifinals in Australia, it looked like Dimitrov was ready to play with the best of them in 2017. Then, just as we thought he’d realize his vast potential, Dimitrov hit a long stretch in the season where he could barely win a match. But before we could give up on him again, he goes and wins his first career Masters title in Cincinnati. In classic Dimitrov form, he followed that up by losing to Andrey Rublev in straight sets in the second round of the US Open. He's currently sixth in the race to London, and looks likely to make it (in large part to several others being injured or having shut it down for the year). If he can get back to his Australian Open and Cincinnati form this fall, Dimitrov can move past his US Open disappointment and become a threat to do some damage at the ATP World Tour finals.