Jakub Mensik takes down sixth seed Jack Draper in Miami

Jack Draper and Andrey Rublev were among a number of seeded players to fall in the round of 64 of the Miami Open on Saturday, while top-seeded Alexander Zverev of Germany cruised to victory.

The sixth-seeded Draper, of Great Britain, lost a grueling 7-6 (2), 7-6 (3) match to Czech Jakub Mensik. Rublev, the Russian who was seeded eighth, also lost in straight sets, 7-5, 6-4 to Zizou Bergs of Belgium.

Draper is ranked a career-high seventh in the world and was coming off his third title win, which came earlier this month in Indian Wells, but he ran into Mensik, who racked up 21 aces.

"The most important thing today was the serve, that was key. I knew in the second set, it was going to be tough at the 30/30 moments and in the tie-break, so I just tried to stay focused. I'm super glad that I kept the focus until the end," Mensik said.

Bergs, who is ranked 51st in the world, picked up his first Top 20 win in edging Rublev. The Belgian had eight aces to six for Rublev, won 65 percent of his second-serve points to 28 percent for the Russian, and led in winners (25-15) and in unforced errors (24-33).

Bergs broke Rublev's serve to clinch the first set, but fell behind 4-2 in the second. He then won four straight games, including two more breaks of the Russian.

Zverev, who lost in the first round in Indian Wells, disposed of Great Britain's Jacob Fearnley, a qualifier, 6-2, 6-4 in about 75 minutes.

Zverev was pleased that his serve has improved. He missed just five of his 47 first serves, according to Infosys ATP Stats.

"I have generally been serving badly, especially after the Australian Open. It's a shot I've worked on since Indian Wells, (and) I had more than two weeks since I lost early there."

Seeded players who lost extended matches included No. 11 Holger Rune of Denmark and No. 13 Ben Shelton.

Rune fell in just over two hours to Reilly Opelka, 4-6, 6-3, 7-6 (5), and Shelton was knocked out by wild card Coleman Wong of Hong Kong 7-6 (3), 2-6, 7-6 (5) in two hours, 16 minutes.

Joao Fonseca of Brazil needed just 71 minutes to defeat 19th-seeded Ugo Humbert of France 6-4, 6-3; No. 25 Alexei Popyrin of Australia bowed out to Roman Safiullin of Russia 6-7 (4), 6-3, 7-5; and fellow Aussie Jordan Thompson eliminated the 28th seed, Giovanni Mpetshi Perricard of France, 7-6 (4), 7-6 (1).

Winning in straight sets were third-seeded Taylor Fritz, No. 10 Alex de Minaur of Australia, 16th seed Frances Tiafoe, 17th seed Arthur Fils of France, No. 29 Matteo Berrettini of Italy and lucky loser Adam Walton of Australia.

Other winners were No. 20 seed Tomas Machac of the Czech Republic and No. 27 Denis Shapovalov of Canada.

--Field Level Media