Tennis star Aryna Sabalenka is breaking her silence on Konstantin Koltsov's passing ... calling it "an unthinkable tragedy" -- while confirming the two had split prior to his death.
Sabalenka -- who dated the former NHL player from 2021 until recently -- penned a heartfelt message on her Instagram page Wednesday evening ... two days after Koltsov had died in Miami.
"Konstantin's death is an unthinkable tragedy," she wrote, "and while we were no longer together, my heart is broken."
"Please respect my privacy and his family's privacy during this difficult time."
It's unclear when Sabalenka and Koltsov officially called things off ... but she had just posted a collage of photos and videos of them together for his birthday last April.
Sabalenka is still expected to compete in this weekend's Miami Open in the wake of the tragedy, although she reportedly will not speak to media members throughout the event. She's slated to play her first match at the tournament on Friday.
As we reported, Koltsov -- an ex-Pittsburgh Penguins first-round pick -- was found dead at around 12:39 AM on Monday at the St. Regis Bal Harbour Resort. Cops suspect he died by suicide ... saying in a statement that no foul play was apparent.
An investigation, however, remains ongoing.