Two-time Wimbledon champion Petra Kvitova says she is terminating her cooperation with coach David Kotyza.
Kvitova announced the move on Twitter and Facebook on Monday.
During her seven years with the coach, Kvitova won a total of 17 WTA titles, including Wimbledon in 2011 and '14.
The Czech has given no reason for the move. She says: "I would like to thank David for the many things he taught me both on and off the court and I wish him all the very best in the future."
It is immediately not clear who will replace Kotyza.
Kvitova was eliminated from the Australian Open by Daria Gavrilova 6-4, 6-4 in the second round, the third time she's fallen before the third round in the past four years.