Novak Djokovic said Roger Federer set the tone for excellence, after the Swiss great announced he would retire from the sport he dominated following next week's Laver Cup in London.
Federer, 41, who redefined the sport with his artistry and grace and collected 20 Grand Slam titles, announced on Thursday that injury issues in the last few years meant that he would call time on his glittering career at the men's team event.
Tributes poured in after Federer's announcement and Djokovic heaped more praise on the player he shared an enduring rivalry with during his own rise to the top of the men's game.
"Roger it's hard to see this day and put into words all that we've shared in this sport together," Djokovic, who surpassed Federer's tally of 20 Grand Slams when he captured the Wimbledon title this year, said on Instagram.
"Over a decade of incredible moments and battles to think back on. Your career has set the tone for what it means to achieve excellence and lead with integrity and poise.
"It's an honour to know you on and off court, and for many years to come. I know that this new chapter will hold amazing things for you, Mirka, the kids, all your loved ones, and Roger fans still have a lot to look forward to.
"From our family to yours, we wish you much joy, health, and prosperity in the future."
Djokovic will join Federer as well as his other great rival -- 22-times major champion Rafael Nadal -- and fellow "Big Four" member Andy Murray, when they play on the same team for the first time at the September 23-25 Laver Cup.
"Looking forward to celebrating your achievements and seeing you in London," Djokovic said.