In a time of increased shuffling in the coaching ranks of professional tennis, the partnership between Victoria Azarenka and her longtime coach Sam Sumyk ended abruptly, at least from Azarenka’s perspective.

During their five years together, Azarenka won two Grand Slam singles titles, rose to No. 1 and then dropped in the rankings last season while struggling with injuries and personal issues.

But Azarenka showed signs of resurgence last month at the Australian Open, and she said she was surprised when Sumyk informed her of his decision to terminate the partnership the day after her fourth-round loss to Dominika Cibulkova.

“I never will forget what we achieved together and always will be grateful, but yeah, it was a bit surprising for me,” Azarenka said in a telephone interview Tuesday from Doha, Qatar. “To me, it’s just sad. There’s no other emotion. There’s no anger. There’s no anything else but just sadness, because it’s like a breakup in a way.”