Alexander Zverev has been knocked out in the second round of the Miami Open ©Getty Images

Germany's third seed Alexander Zverev was dumped out of the Miami Open in the biggest shock yet, losing in three sets against Finnish player Emil Ruusuvuori.

Zverev went down to the 21-year-old 1-6, 6-3, 6-1 in the second round, making him the highest seed to be knocked out so far.

The German had received a bye through round one at Hard Rock Stadium in Florida.

Australia's James Duckworth knocked out another top-15 player, defeating eighth seed David Goffin 6-3, 6-1, while Britain's Cameron Norrie beat ninth seed Grigor Dimitrov of Bulgaria 7-5, 7-5.

The United States' Frances Tiafoe came from a set down to turn over 19th seed Dan Evans of Britain 6-7 (5-7), 6-3, 6-3 and Sweden's Mikael Ymer knocked out 27th seed Nikoloz Basilashvili of Georgia 6-3, 4-6, 6-3.

Ymer will play Ruusuvuori next.

Felix Auger-Aliassime of Canada, seeded 11th, went through in straight sets against Pierre-Hugues Herbert of France and 14th seed Karen Khachanov of Russia also needed just two sets to beat Germany's Yannick Hanfmann.

John Isner ended the day in an all-American tie against Mackenzie McDonald, defeating him 2-6, 6-3, 7-5.

In the women's singles, Japan's four-time Grand Slam champion Naomi Osaka made a winning start, beating Australia's Ajla Tomljanović 7-6 (7-3), 6-4.

Czech sixth seed Karolina Plíšková went through in straight sets too after a 6-2, 6-1 victory over China's Zheng Saisai and Canadian eighth seed Bianca Andreescu defeated Czech Tereza Martincová 7-6 (7-5), 6-2.

Fourth-seeded American Sofia Kenin fought back to overcome Germany's Andrea Petkovic 6-7 (6-8), 6-1, 6-3, while 12th seed Garbiñe Muguruza of Spain is through to round three as well after a 6-4, 6-1 victory over China's Wang Xinyu.

The biggest shock of the day in the women's singles came when Ludmilla Samsonova thrashed Dutch 10th seed Kiki Bertens 6-2, 6-1.

Russia's Samsonova had to qualify for the main draw, but has since recorded two straight-sets wins.

In another upset, US player Jennifer Brady suffered a 3-6, 6-4, 6-1 defeat to Spain's Sara Sorribes Tormo.

Other seeds to be knocked out were Croatian 20th seed Petra Martić and Kazakhstan's 26th seed Yulia Putintseva.

Martić went from a set up to lose to Russian Anna Kalinskaya 5-7, 6-2, 7-6 (7-4); Putintseva suffered the same fate against Serbia's Nina Stojanović, going down 5-7, 7-5, 6-2.

The Women's Tennis Association 1000 and Association of Tennis Professionals Masters 1000 tournament continues tomorrow.