British number one Johanna Konta has split from her coach Wim Fissette after less than a year together and will not play again this season.
The 26-year-old, who has a foot injury, did not qualify for this month's WTA Finals in Singapore and will not play in the WTA Elite Trophy the week after.
"Wim Fissette and I have mutually decided to end our working relationship," she said on Wednesday.
"My foot is improving but it is still advisable to rest it further."
She added: "Things ended very amicably and I wish Wim all the best. We've achieved a lot together and I want to thank him for all his patience, hard work and expertise.
Konta linked up with Belgian Fissette before the 2017 season after parting company with Esteban Carril at the end of 2016.
She will continue to work with hitting partner Andrew Fitzpatrick, strength and conditioning specialist Gill Myburgh, physio Milly Mirkovic and mental coach Elena Sosa.
"I will be working with my team over the coming weeks to find the right way forward for me and my tennis," she said in a statement.
"The goal is to get a new coach or coaches in place as soon as possible but the focus will be on making the right decision rather than a quick decision."
Konta's poor end to the season
Konta won the biggest title of her career at the Miami Open in April under Fissette's guidance and then made the semi-finals of Wimbledon to climb to fourth in the world rankings.
But her season went rapidly downhill following her defeat in the last four by Venus Williams at Wimbledon, winning just two matches and losing her last five since that semi-final in July.
The five-match losing streak, coupled with a foot injury picked up before the Hong Kong Open earlier this month, saw her narrowly miss out on the WTA Finals in Singapore for the second year in a row.
Despite missing out on the WTA Finals, which begin on 22 October, Konta was still in line to qualify for the WTA Elite Trophy in Zhuhai, China, and could have travelled to Singapore as an alternate.
"Both are amazing events and I will really miss being part of them but I want to make sure I am fully fit to start preparations for what I hope will be an exciting 2018 season," she said.
BBC tennis correspondent Russell Fuller
The split appears amicable, but is also a sign Konta feels in need of fresh impetus to continue her rapid rise of the past two years.
Just as when she parted with Esteban Carril at the end of 2016, this is not without risk. Five consecutive defeats are a dispiriting way to end a season, but Konta enjoyed huge success under Fissette's guidance.
She won in Sydney in January, Miami in April, and then climbed to number four in the rankings after becoming the first British woman for 39 years to reach the Wimbledon semi-finals.
Konta will now consider her options at a time of the year when many coaches tend to come on to the market. She has the advantage of being the first leading player to 'advertise' a vacancy.
It would be handy to strike up a partnership before pre-season training gets into full swing in November. As things stand, Konta is unlikely to head off to the sun: preferring instead to stay at home to prepare for 2018.
Konta's foot problem means an early end to the season, but after a break, she is likely to start training for next year in the UK.