Novak Djokovic knows there's a chance he may not have played his opening match at the Australian Open before Andy Murray is out of the tournament. Perhaps even finished on the tour.
Their careers have long been intertwined. They're both 31 and have birthdays a week apart in May, and they've played each other 36 times at the elite level.
Djokovic leads those 25-11, including a 4-0 record in finals at the Australian Open, where Murray has been a five-time finalist but never won the title.
They had a practice match together in Melbourne Park on the eve of Murray's teary news conference Friday, where he revealed the pain from his surgically-repaired right hip was so bad that he'd decided to retire after attempting one more run at Wimbledon — if he can make it that far.
Murray was noticeably limping between points and only won two games in almost two full sets, but Djokovic on Sunday denied he'd taken it any easier on his long-time friend. It's not the way they operate.
"I wasn't, no. To be honest, I wasn't," top-ranked Djokovic said. "But I did see, it was very obvious for everyone, you didn't need to be on court to notice that he's struggling.
"We've seen so many years of Andy Murray being one of the fittest guys on the tour, running around the court, getting always an extra ball back. I think to that extent, we are kind of similar."
Djokovic has six Australian Open titles, a record he shared with two-time defending champion Roger Federer and Roy Emerson. Djokovic and Federer are on opposite sides of the draw, and can only meet in the final. Murray is in Federer's half, but even he concedes he's unlikely to get past No. 22-seeded Roberto Bautista Agut on Monday night.
Djokovic isn't in action until Day 2, when he opens against U.S. qualifier Mitchell Krueger. As winner of the last two majors, he's a strong contender to win in Melbourne Park again and become the first man with three streaks of three or more consecutive Grand Slam championships.
His 14 majors so far place him third behind 37-year-old Federer (20) and 32-year-old Rafael Nadal (17), but he's likely got more years to play on the circuit.
Murray's career is expected to be finished in a matter of months. He didn't tally as many titles as the other members of the Big Four, but he broke decades-long droughts for British men in majors and at Wimbledon, and became the first player to win consecutive singles gold medals at the Olympics.
"Our trajectory to the professional tennis world was pretty much similar," Djokovic said. "We've grown together playing junior events. We played lots of epic matches in the professional circuit (and) our games are quite alike.
"Obviously to see him struggle so much and go through so much pain, it's very sad and it hurts me as his longtime friend, colleague, rival."
Djokovic said he was proud of the kind of relationship he and Murray had fostered, and he was sorry to see his friend set to leave the tour.
"It's sad for me, but for all sport, because Andy is a very respected and likable guy around the locker room," Djokovic said. "He's a great champion. He's a legend of this sport, without a doubt — multiple Grand Slam winner, two golds from Olympic Games, Davis Cup. He's had it all.
"He touched us all definitely. I wish him a painless future in whatever shape or form that is, on or off the court."
