Rising Spanish star Rafael Jodar was warned for unsportsmanlike conduct after shouting an expletive at a ballboy in the fourth round of the Shanghai Masters on Wednesday.
Jodar, 20, was trailing Botic van de Zandschulp after losing the first set on a tie-break when he shouted in Spanish: "Give me the ******* towel!"
He had fired a shot just long to lose a break point in the first game of the second set.
Jodar was swiftly issued a warning for unsportsmanlike conduct, a violation of the ATP rulebook, by Ecuadoran chair umpire Jimmy Pinoargote.
The two had a brief exchange in Spanish as Jodar complained to Pinoargote that his request for a towel was being ignored.
Pinoargote responded that he understood but could not excuse Jodar's language.
"Ask me, and I'll ask him," Pinoargote said.
"Not like that – that's not how we speak to them."
When Jodar asked Pinoargote, "What did I say?", and the umpire responded: "I can't repeat it. You know what you said."
Jodar went on to beat van de Zandschulp 6-7 (4/7), 6-4, 6-2.
The world number 13 is having a breakout season after starting at 168th.
He will face Casper Ruud in the Shanghai quarterfinals after the Norwegian advanced when Felix Auger-Aliassime retired injured from their fourth-round match.
Ball boys and girls are stationed around the court to fetch loose balls and toss them to players during service games. They also hand players towels between points.