Alejandro Davidovich Fokina hit 24 winners and recorded a huge upset when he took down third-seeded Daniil Medvedev 6-4, 1-6, 6-2 on Thursday in the second round of the National Bank Open at Montreal.

It marks the first time Davidovich Fokina has defeated Medvedev in five meetings. It also is his third career win over a Top 5 player.

Two other Top 10 seeds lost in Thursday's second round.

Japan's Kei Nishikori swept to a 6-4, 6-4 upset of eighth-seeded Greek Stefanos Tsitsipas, and qualifier Brandon Nakashima registered a 6-2, 6-7 (5), 6-1 victory over No. 10 seed Tommy Paul in an all-American clash.

Davidovich Fokina converted 4 of 7 break-point opportunities while stunning Medvedev. The Spaniard also won 50 percent (16 of 32) of his second-serve points.

"To have this opportunity to beat a player like Daniil gives me a lot of strength and power to continue to grow," Davidovich Fokina said. "I am very happy with this win. At the end of the set it is not easy to close a match and less with Daniil because he is a very solid player. I had to be calm today and not think about the result."

Medvedev had a 9-3 edge in aces. The Russian had 27 winners against 17 unforced errors. Davidovich Fokina made 15 unforced errors.

Davidovich Fokina will next face Italy's Matteo Arnaldi, who posted a 7-5, 7-5 win over Russian Karen Khachanov, the No. 16 seed.

As for Nishikori, he only had 13 winners against Tsitsipas but had solid success at the net by winning 11 of 12 points (91.7 percent) during a 79-minute victory.

"Beating Stef is not easy and for me it is a great win," Nishikori said. "I stayed aggressive and was not missing too many balls today."

Tsitsipas had a 9-2 edge in aces and delivered 21 winners in defeat.

Nishikori next faces Portugal's Nuno Borges, who rallied for a 3-6, 7-6 (2), 7-6 (4) victory over 12th-seeded Ugo Humbert of France.

Nakashima had 26 winners and just 11 unforced errors while improving to 3-0 all-time against Paul.

Nakashima had a 9-4 edge in aces and saved both break points. Paul had 28 winners and 23 unforced errors.

Nakashima next faces No. 5 seed Andrey Rublev of Russia. Rublev defeated Thomas Martin Etcheverry of Argentina 7-6 (3), 6-2.

No. 11 Ben Shelton also was upset as Aussie Alexei Popyrin didn't face a single break point during a 6-4, 7-6 (4) victory.

Top-seeded Jannik Sinner cruised to a 6-2, 6-4 victory over Borna Coric of Croatia, and No. 2 Alexander Zverev of Germany rolled to a 6-1, 6-1 win over Australia's Jordan Thompson.

No. 6 Casper Ruud of Norway outlasted Australian qualifier James Duckworth 6-2, 6-7 (5), 6-3, while No. 7 Grigor Dimitrov of Bulgaria blew out Australia qualifier Rinky Hijikata 6-1, 6-0.

No. 13 Holger Rune of Denmark sailed to a 6-1, 6-3 victory over Spain's Pablo Carreno Busta. No. 15 Alejandro Tabilo of Chile was a 6-4, 6-2 winner over Italy's Lorenzo Sonego.

France's Arthur Rinderknech led Italy's Flavio Cobillo 3-0 in the first set when their match was halted due to rain and suspended until Friday. Two other matches were postponed until Friday: ninth-seeded Taylor Fritz vs. Sebastian Korda in an all-U.S. showdown, and fourth-seeded Hubert Hurkacz of Poland vs. Australian qualifier Thanasi Kokkinakis.

--Field Level Media