Top-ranked Novak Djokovic dropped a hint that he may split with coach Boris Becker on Thursday, as Nick Kyrgios was hit with a big fine for his Shanghai Masters meltdown.
Djokovic, who says he is taking a fresh mental approach after struggling in recent months, revealed that he had made no plans about retaining Becker in his team next year.
"We are still working (together), yeah... for now the plan is the rest of the season, what's left, indoor tournaments," said Djokovic, after reaching the Shanghai quarter-finals.
Asked what would happen next year, the defending champion said: "We still haven't talked about it."
Becker joined Djokovic's coaching team at the start of 2014, helping him win six of his 12 Grand Slam titles and put together one of the all-time great seasons last year.
Speculation about their partnership has grown since the Serb suffered a crisis of motivation and a series of injuries since completing a career Grand Slam at the French Open.
Djokovic lost in Wimbledon's third round and in round one at the Olympics before reaching the US Open final, while also enduring wrist and elbow problems and admitting "private issues".
"I don't think about any trophies or number ones in the world, rankings, anything like that. It's completely different," he said this week, explaining his new approach.
Djokovic skipped last week's China Open with his wrist injury but he was in impeccable form as he dismantled Canadian qualifier Vasek Pospisil 6-4, 6-4 on Thursday.
Second-ranked Andy Murray, who is gunning for Djokovic's world number one crown, was even more impressive as he walloped Lucas Pouille 6-1, 6-3.
Murray didn't face any break points against France's Pouille as, like Djokovic, he raced into the last-eight without dropping a set.
Separately Australia's Kyrgios received a $16,500 fine after his extraordinary 6-3, 6-1 defeat to 110th-ranked Mischa Zverev where he tanked points and argued with fans.
The combustible world number 14 received the maximum $10,000 fine for "lack of best efforts", plus $5,000 for abusing a spectator and another $1,500 for unsportsmanlike conduct.
Trouble-prone Kyrgios, 21, patted a slow serve into his opponent's court and failed to contest several points in his second-round defeat on Wednesday.
Kyrgios also clashed with the chair umpire and fans, received a code violation for swearing and had a heated argument with one spectator when he was facing match points.
In further action on Thursday, America's Jack Sock beat Milos Raonic 0-6, 6-4, 7-6 (10/8), ending a run of eight straight defeats to the Canadian fifth seed.
Last year's finalist Jo-Wilfried Tsonga ousted racquet-smashing teenager Alexander Zverev 6-7 (4/7), 6-2, 7-5 to set up a last-eight clash with Roberto Bautista.
Alexander's 110th-ranked elder brother, Mischa, also beat Marcel Granollers 6-7 (4/7), 6-4, 6-1 to earn a meeting with Djokovic.
Later, France's Gilles Simon stunned US Open champion Stan Wawrinka 6-4, 6-4. He will play Sock in the quarter-finals on Friday.
Twelfth-ranked David Goffin beat Gael Monfils 4-6, 6-4, 6-2 for his first win against the Frenchman and a quarter-final match-up with the in-form Murray.