American qualifier Frances Tiafoe advanced to the second round of the Shanghai Masters by beating Benoit Paire 6-4 6-4.
The 92nd-ranked Tiafoe was playing in his first main draw match since a five-set loss to Roger Federer at the US Open.
Chung Hyeon also advanced on Monday, defeating ninth-seeded Roberto Bautista Agut 6-4 6-3. Chung saved all four break points he faced.
"Today, I was trying to stay calm all the time in the match," said Chung, who only won one game when he played Bautista Agut in Dubai in 2016. "I won today so I did everything good."
Also, Feliciano Lopez advanced by beating Ivo Karlovic 7-6 (7-1) 7-6 (7-6).
Federer, who won the title in Shanghai in 2004, will play his opening match on Wednesday. The Australian Open and Wimbledon champion hasn't played at an official tournament since losing in the US Open quarter-finals.
"I'm playing just the big tournaments now," Federer said. "I've been practising for hours on the centre court. I'm here for a reason. I'm here for a purpose. Hopefully to do well and winning the tournament.
Federer will play either Diego Schwartzman or Australian qualifier Jordan Thompson in his first match.
