On Tuesday, Milos Raonic became the seventh player ranked in the top 10 to withdraw from the tournament, right before fellow seeded players David Goffin, Tomas Berdych and Jack Sock were knocked out in first-round matches. Juan Martin del Potro advanced to the second round with a 3-6, 7-6 (1), 6-0 upset of the 10th-seeded Berdych. Yuichi Sugita followed with a 7-5, 6-4 victory over the 13th-seeded Sock. Del Potro shook off a first-set loss, jumping out to a 4-1 lead in the second set before settling for a win in the tiebreak, which he led 5-0 and clinched with an ace. He built on his momentum by rolling through the third set against the Wimbledon semifinalist, improving to 12-0 in first-round matches this season.

Berdych was playing his first match since withdrawing from last week's Rogers Cup in Montreal with a rib injury. Sugita clinched his win by breaking Sock with a shot that clipped the baseline, a call that was confirmed by review. "I tried to make a serve and the first shot is the most important thing," Sugita said. "I tried to go into the net and be aggressive on the court." The ninth-seeded Goffin became the first seeded man to be knocked out in Cincinnati, falling to Nick Kyrgios, 2-6, 3-6. Kyrgios will meet qualifier Alexandr Dolgopolov in the second round after Dolgopolov defeated Kevin Anderson 6-4, 7-6 (6). Also, Karen Khachanov beat Diego Schwartzman 6-1, 1-6, 6-3.