The former ice hockey star spent three seasons with the Pittsburgh Penguins in the mid-2000s and competed at two Winter Olympics for Belarus.
His tragic death was announced by Russian ice hockey club Salavat Yulaev, who wrote: “It is with deep sorrow that we inform you that the coach of Salavat Yulaev, Konstantin Koltsov, has passed away.
“He was a strong and cheerful person, he was loved and respected by players, colleagues, and fans. Konstantin Evgenievich forever wrote himself into the history of our club.
“Koltsov won the Russian Championship and the Gagarin Cup as part of Salavat Yulaev, and did a great job on the team’s coaching staff.
“May his memory burn bright.”
It is understood Koltsov and two-time Australian Open champion Sabalenka were dating since 2001.
An Instagram post from Sabalenka, posted on Koltsov’s last birthday, read: “I love you @koltsov2021. Happy birthday my love. You are my dearest person, my best friend and my strongest support.
“Peace be with you, strength, patience and health. I hope we will have everything we planned I love you.”
Koltsov is reported to have been a father of three from a previous relationship.
Sabalenka, who was second-seed in Miami following her recent successful defence of the Australian Open title, has been withdrawn from practice schedules.
The 25-year-old suffered another tragedy five years ago when her father Sergey died suddenly at the age of 43.
