A winner of this tournament in two of the past three years, Williams is coming off a disappointing Wimbledon loss to Alizé Cornet in the round of 32. Williams has had a difficult time of late, but last year's U.S. Open champion is always a threat to win, especially on hard courts.
The fourth-ranked player in the world beat Eugenie Bouchard quite handily in the Wimbledon final. Kvitova is set to be the third seed at the Rogers Cup as she hunts for her first hard-court title in 2014.
The French Open champion is trying to win her first U.S. Open since 2006. Montreal is the next step on that path, as Sharapova will be the fifth seed in a tournament she has never won.
Playing some of the best tennis of her life, the 20-year-old returns to her hometown with the chance to add to her already impressive résumé. Bouchard withdrew from the Citi Open in Washington, but more because she wanted to rest up for this tournament than because of injury.
After her breakup with golfer Rory McIlroy, Wozniacki lost her first match at the French Open but has since won a tournament, July's Istanbul Cup. Wozniacki, the champion of this event in 2010, has come closer to winning the hard-court U.S. Open than any other Grand Slam.