Novak Djokovic choked back tears as he paid tribute to Kobe Bryant.

After moving within two wins of an eighth Australian Open title with a win over Milos Raonic, Djokovic wore a green jacket with the letters K B and the numbers 8 and 24 embroidered on the chest, with a red heart under the numbers.

In an on-court interview with John McEnroe, the 16-time major winner was visibly upset when he spoke about his friendship with Bryant. At a later news conference, Djokovic said he was “heartbroken.”

“He was one of the greatest athletes of all time. He inspired myself and many, many other people around the world,” Djokovic said. “I had the good fortune to have a personal relationship with him over the last 10 years. When I needed some advice, some support, he was there for me.”

“He was my mentor, my friend. And It’s just heartbreaking to hear what has happened to him and his daughter.”

He had to pause and stop speaking for a while before he continued the interview.

Bryant, an 18-time NBA All-Star with the Los Angeles Lakers, died Sunday with his 13-year-old daughter, Gianna, in a helicopter crash near Calabasas, California, along with seven others. He was 41.