Fabio Fognini of Italy bumped into the Chinese wild card who beat him and gave an obscene gesture to the crowd at the Shanghai Masters on Tuesday.
Fognini, a 10-year professional ranked 17th in the world, was upset by the 553rd-ranked Wang Chuhan, who was making his ATP Tour debut.
After Wang won 7-6 (5), 6-4, Fognini gave Wang a little shove with his arm as they crossed paths, then flashed his middle finger to the crowd upon exiting.
The Italian, known for his fiery temper, has lost five of his last six matches since reaching the Cincinnati quarterfinals in August.
Wang next plays Tunisian qualifier Malek Jaziri for a spot in the third round.
In other matches, Russian Mikhail Youzhny eliminated 12th-seeded Ernests Gulbis of Latvia 6-4, 6-1, and Feliciano Lopez of Spain beat Thanasi Kokkinakis of Australia 6-7 (12), 6-3, 6-4 to set up a second-round match with Rafael Nadal, who has been diagnosed with appendicitis.