Defending champion Daniil Medvedev said missing one key opportunity had cost him a spot in the Shanghai Masters' fourth round after he was knocked out in straight sets by 26th-ranked Sebastian Korda on Sunday.
The Russian fell apart in the second set after Korda won the first on a tiebreaker taken to the brink, with the match finishing 7-6 (10/8), 6-2.
"I should have won the tiebreak but didn't," said the world number three afterwards.
Medvedev had said the game would be "interesting" for him beforehand, referencing his loss to Korda in their last meeting.
At a press conference after Sunday's match, looking deflated, he said he would sum up his time in China as "not amazing".
He made the final of Beijing's China Open this week but lost to Italian Jannik Sinner.
Earlier, world number nine Casper Ruud continued his smooth progress through the tournament with another straight-sets win, this time against the United States' Christopher Eubanks.
Ruud appeared in control throughout against the 32nd-ranked American, with the third-round match ending 6-4, 6-2.
World number seven Andrey Rublev is through
to the third round after defeating France's Quentin Halys 6-4, 7-5.
Two top-20 players exited the tournament in the second round on Sunday.
Britain's 16th-ranked Cameron Norrie was defeated by the United States' JJ Wolf, ranked 51st.