The 29-year-old American, who is currently No. 147 in the ATP Rankings, won 87 per cent of his first-serve points and saved the only break point he faced to advance after one hour and 22 minutes.
Sock has won two of his four ATP Tour singles titles in the United States and is trying to add another this week. He has won on some of the sport’s biggest stages in the past, including his run to the 2017 Rolex Paris Masters trophy.
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Next up for the wild card will be top seed Taylor Fritz. They have met four times on the ATP Tour, splitting those clashes.
“I knew going into the match it was going to be tough. Sandgren of course has been Top 50 in the world. He’s made big runs in Australia and he’s got a very high level,” Giron said. “Going into the match I was looking for my first win of the year in singles and so I’m happy to get that. Going into the match I knew it was going to be hard. I knew I would have to play well and I did a good job of playing well on the important points.”
The upset of the day came when Austrian qualifier Jurij Rodionov battled past in-form American Maxime Cressy 7-6(3), 4-6, 6-1. Cressy, known for his serve-and-volley style, hit 20 aces, but Rodionov saved two of the three break points he faced to reach the second round, in which he will play Vasek Pospisil.
The Canadian qualifier eliminated wild card Caleb Chakravarthi 6-1, 6-0. The American competes for Southern Methodist University, the host of the ATP 250 event.