Konstantin Koltsov, the boyfriend of Australian Open champion Aryna Sabalenka, has died at the age of 42.
Koltsov played for the Belarus national team during his ice hockey days, representing the country in the 2002 and 2010 Winter Olympics.
He also spent parts of three seasons with the NFL's Pittsburgh Penguins from 2002 and 2006, too.
Sabalenka is currently in Miami preparing for the Miami Open and Koltsov, according to the Daily Mail, joined her in Florida prior to his sudden death.
Konstantin Koltsov, the boyfriend of Aryna Sabalenka, has died at the age of 42
Former club Salavat Yulaev Ufa confirmed his death on Telegram.
"It is with deep sorrow that we inform you that the coach of Salavat Yulaev, Konstantin Koltsov, has passed away," a statement read.
"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."
The death of Sabalenka's boyfriend comes just five years after her father died.
Like Koltsov, he also played professional ice hockey.
According to People magazine, Sabalenka and Koltsov first started dating in June 2021 - with frequent pictures of the pair published in the years since.
Koltsov was in Australia in January as Sabalenka won the Australian Open for the second year on the trot.
She has previously taken to social media to say: "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."
It is currently unclear if Sabalenka will play in the Miami Open following the devastating development.
Fans on X have paid tribute to Koltsov, with one user saying: "Just horrible news, absolutely horrible."
Konstantin Koltsov has died in Miami
A second said: "Wow. Looks like the death of former Belarusian Olympian and Pittsburgh Penguins hockey star Konstantin Koltsov has been confirmed by his former Russian team, Salavat Yulaev.
"Koltsov was also the long-time boyfriend of Aryna Sabalenka. Just tragic for everyone involved."
Konstantin Koltsov and Aryna Sabalenka started dating back in June 2021
A third said: "Heartbroken for Aryna. She lost her father a few years ago… and now this.
"Send Aryna & Koltsov’s family your prayers. They’re going to need them."