Ruusuvuori went 4-for-4 on break points on his own serve, and he converted his only break point on Hurkacz's serve for a 3-2 lead in the first set.
Sixth-seeded Denis Shapovalov of Canada also stumbled in the second round, falling 6-2, 6-7 (5), 6-3 to the United States' J.J. Wolf. Japan's Yoshihito Nishioka topped 11th-seeded Alex de Minaur of Australia 3-6, 7-6 (6), 6-2, and the United States' Sebastian Korda routed 12th-seeded Sebastian Baez of Argentina 6-1, 6-4.
Nick Kyrgios, who made his first career Grand Slam final last month at Wimbledon, beat 14th-seeded Tommy Paul of the United States 6-3, 6-4.
Other second-round winners included four Americans, third-seeded Taylor Fritz, fourth-seeded Reilly Opelka, 10th-seeded Frances Tiafoe and 13th-seeded Maxime Cressy. Also advancing were fifth-seeded Grigor Dimitrov of Bulgaria, ninth-seeded Holger Rune of Denmark and Mikael Ymer of Sweden.
Top-seeded Daniil Medvedev of Russia rolled past Australia's Rinky Hijikata 6-4, 6-3 to reach the quarterfinals in Los Cabos, Mexico.
In other second-round action, second-seeded Felix Auger-Aliassime of Canada earned a 6-3, 7-5 win over Mexico wild card Alex Hernandez, and third-seeded Cameron Norrie of Great Britain crushed Chun-Hsin Tseng of Taiwan 6-3, 6-0.
Fourth-seeded Miomir Kecmanovic of Serbia cruised past Australia's Jordan Thompson 6-4, 6-2. Sixth-seeded Brandon Nakashima of the United States dumped Australia's Max Purcell 6-3, 6-3, and the United States' Steve Johnson overtook seventh-seeded Thanasi Kokkinakis of Australia 6-7 (3), 6-4, 6-4.
Lithuania's Ricardas Berankis got past Facundo Bagnis of Argentina 7-6 (4), 6-3.
