GRIGOR DIMITROV (AGE: 26), BUL
World ranking: 9
The Bulgarian dominated the field to win his first Masters 1000 tournament in Cincinnati last week. He had five straight-sets victories and held serve 52 out of 53 times.
Dimitrov has long been compared to Roger Federer and covers the court with the same ease and seeming effortlessness. Under the tutelage of Dani Vallverdu, Dimitrov is having the best year of his career, cracking the top 10 and competing at a consistently high level.
With his improved mental game and shrewd use of tactics, the seventh-seed has matured into a player capable of winning the US Open title.
DENIS SHAPOVALOV (18), CAN
World ranking: 69
The teenager electrified the tennis world by upsetting Juan Martín del Potro and Rafael Nadal in Montreal this month. His run to the semi-finals heralded the arrival of a future champion, as Shapovalov, a left-handed Canadian, displayed remarkable grit and spirit in addition to incredible ball-striking.
Shapovalov, who earned a spot in the Open main draw through qualifying, has a strong serve and a rock-solid one-handed backhand, but he looks to dominate points with his best shot, an inside-out lefty forehand that he used to bludgeon the Nadal backhand.
Shapovalov looks like the teenager he is, but he plays with maturity and self-belief.
MADISON KEYS (22), USA
World ranking: 16
Keys, seeded 15th, has one of the game's best serves, which she hits with a beautiful, flowing motion that generates tremendous speed and spin.
Her ground game is balanced and powerful as she looks to dominate her opponent with flat, penetrating strokes that allow her to move forward and control court positioning.
Since returning from wrist surgery late last year, Keys looks more comfortable attacking the net. With coach Lindsay Davenport's steadying influence, she seems ready to navigate the treacherous path through a Grand Slam draw.
EKATERINA MAKAROVA (29), RUS
World ranking: 40
She has had an excellent North American hard-court season, winning the Washington Open and scoring victories over world No. 2 Simona Halep, No. 6 Angelique Kerber and No. 7 Johanna Konta.
Makarova uses a wicked left-handed slice serve to pull opponents off the court, then hits her best shot, a two-handed backhand, into the open court, a devastating one-two punch.
Ranked 38th, Makarova will be unseeded in New York, but she is playing well enough to score a few upsets. After winning the Wimbledon doubles title with Elena Vesnina last month, she has set her sights on winning her first Grand Slam singles title.