World No. 2 Karolina Pliskova has announced she will no longer be working with coach Conchita Martinez.
Martinez, herself a former World No. 2 and Wimbledon champion, joined Pliskova's coaching staff in 2018.
The Czech Republic's Pliskova, who lost her semifinal at the WTA Finals to World No. 1 and eventual winner Ashleigh Barty last week, took to Instagram to share the news.
"I decided I will no longer work with Conchita," the 27-year-old wrote. "It was a tough decision, as the season was great.
"Thank you for all this year, and I wish you only the best."
Pliskova lifted trophies in Brisbane, Eastbourne and Zhengzhou this year, as well as at the Italian Open.
She was runner-up at the 2016 US Open and held the World No. 1 ranking in 2017 before Martinez joined her team.
Martinez previously worked with Garbine Muguruza, another former World No. 1, and helped her fellow Spaniard to the Wimbledon title in 2017.