SHANGHAI (AP) — Four American players pulled off upsets at the Shanghai Masters on Monday. A fifth wasn't so lucky.

Sam Querrey, Mackenzie McDonald, Bradley Klahn and Taylor Fritz all posted wins in the first round of the tournament, while Frances Tiafoe lost his match.

Perhaps the most surprising win came from the 81st-ranked McDonald, who defeated 14th-seeded Milos Raonic 6-3, 5-7, 6-3.

"Definitely my biggest win to date," said McDonald, a qualifier into the main draw. "I thought I played great tennis and I could feel all the improvements I've had over the last few months and was happy I could put it together tonight."

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It was the second meeting between the two. Raonic won their fourth-round encounter at Wimbledon in four sets in July.

Klahn, also a qualifier and making his first appearance in Shanghai, defeated Nick Kyrgios 4-6, 6-4, 6-3. The talented but erratic Kyrgios has played in Shanghai four times with his best showing being two second-round finishes.

Querrey upset ninth-seeded Diego Schwartzman 6-3, 6-4, while Fritz beat Robin Haase 6-3, 7-6 (3). The pair will face each other in the next round.

Tiafoe, however, lost to Matthew Ebden 3-6, 6-4, 6-3.

Also, 10th-seeded Stefanos Tsitsipas beat Gael Monfils 7-6 (4), 4-6, 6-4 and 13th-seeded Borna Coric of Croatia defeated wild-card entry Stan Wawrinka 4-6, 6-4, 6-3.

The 20-year-old Tsitsipas is one of the fastest rising players on tour. He started the season ranked No. 91 and is currently sitting at No. 15.

"I have improved a lot since last year physically, mentally," said Tsitsipas, who was a qualifier last year but is seeded this year. "My game has changed. I am more aggressive now. I'm actually stronger."

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