Johanna Konta and Milos Raonic split from their coaches
Johanna Konta has split from Spanish coach Esteban Carril, while Milos Roanic has parted ways with Carlos Moya.
The news comes as a surprise given the 25-year-old's incredible rise under the guidance of Carril.
"After two-and-a-half successful years working together we have mutually agreed to explore new options," said Konta.
"Once things are confirmed we will share the new set-up."
Johanna Konta (GBR) of United Kingdom celebratesReuters
Konta turned to Carril, who is the director of an academy in Gijon, after having her funding cut by the Lawn Tennis Association.
At that stage, Konta was ranked outside the top 100, but her rapid rise began in the summer of 2015 when she reached the fourth round of the US Open as a qualifier.
She began 2016 with a stunning run to the semi-finals of the Australian Open and has continued to climb the rankings since, finishing the year as the first British woman to be ranked in the top 10 since Jo Durie 32 years ago.
Carril also introduced Konta to mental coach Juan Coto, whose influence has arguably been even more important in helping her overcome performance anxiety.
Konta, who was named the WTA's most improved player for 2016, will begin next season at the Shenzhen Open in China, starting on January 1.
'Thanks for helping get the best out of me'
News of the split comes hot on the heels of Raonic's announcement that he will no longer be working with former world number one Moya, another Spaniard.
Canada's Milos Raonic returns against Britain's Andy Murray during their men's semi-final singles match on day seven of the ATP World Tour Finals tennis tournament in London on November 19, 2016AFP
Moya joined Raonic's team at the start of the year and helped the Canadian to the best season of his career, capped by a Wimbledon final appearance and ascent to world number three.
Raonic wrote on Instagram: "Thank you to Carlos Moya for helping me tremendously this year, alongside my team, to get the best out of me.
"Under Carlos' direction and tutelage I have played my best yet to date. We will no longer be continuing our coaching relationship but remain close friends. I wish him all the best."
Raonic, who was also advised by John McEnroe this year, will continue to work with his main coach Riccardo Piatti.
The news also comes after Madison Keys ended her coaching agreement with Thomas Hogstedt after the best season of her career.
As well as Raonic and Konta, Madison Keys, Elina Svitolina, Kristina Pliskova and David Goffin have all parted company with coaches after career-best years.
Reporting by PA Sport/Eurosport
This seems pretty brutal from Konta if the split is simply down to on-court performance, given her incredible year. However, if there is a time to do it, now is the moment – the start of the off-season.
Similarly, it is perhaps less surprising when taking into account that much of Konta's game has improved on the psychological side of things. Eurosport commentator Jeremy Bates, the former British No 1 and LTA Head Women’s Coach, said earlier this year: "I’ve known Jo for a long time and she’s always been a worker, completely dedicated to the sport. But the big difference is that she has matured with being on the tour, and she has become an awful lot stronger mentally."
So perhaps Konta, who has always had a strong game, feels her improvement has been more down to Coto than Carri. Either way, both sides are keeping the reasons for the split private so it will be interesting to see how this affects her form come the Australian Open in January and whether she can keep hold of her top-10 berth.