Johanna Konta has parted company with her coach Esteban Carril at the end of a year in which she made her debut in the world's top 10.
The British number one had been based in Gijon in Spain with Carril and Jose-Manuel Garcia.
"After two and a half successful years working together we have mutually agreed to explore new options," said 25-year-old Konta.
"Once things are confirmed we will share the new set-up."
Konta, who is preparing for the new season at the National Tennis Centre in Roehampton, reached the semi-finals of the Australian Open in January and won her first WTA Tour title at Stanford in June.
Ranked world number 147 in June 2015, she climbed to a career-high position of ninth and is currently in 10th place.
She won the WTA's most improved player of the year award for 2016.
Konta became the first British woman to reach the top 10 of the world rankings since Jo Durie achieved the feat in 1984.
BBC tennis correspondent Russell Fuller
The split comes as quite a surprise given Konta's stellar year. With the help of Carril and Garcia, the British number one has transformed her career and only time will tell how the decision might affect her in 2017.
Konta is also trying to come to terms with the terrible loss of her mental coach Juan Coto, who died suddenly three weeks ago.
Juan Coto played a significant role in Konta's climb from 150 in the world rankings and, as a friend of Carril, formed an integral part of the coaching team.
Konta says she has been much better at keeping the sport in perspective since they started working together. In that time, she has become very adept at closing out tight matches, and a player very worthy of her position in the world's top 10.