Novak Djokovic has fielded plenty of retirement questions over the last few years. Aged 38, he's still as motivated as ever by the prospect of winning a historic 25th Major title. But it's been two years since he even reached a final at Grand Slam level, and some are wondering what he'll do next.

The world No. 7 could well claim another Major crown this fortnight at the US Open, where he got off to a winning start by beating up-and-coming American teenage Learner Tien in the first round. But Djokovic also has one eye on his post-playing career, and he revealed he'd be keen to coach another teenage sensation.

In a new US Open video, players were made to answer questions, before coming up with a query for the next star. And Joao Fonseca asked Djokovic: "What's your plan after you retire from tennis?"

The Olympic gold medallist threw in a curveball answer, giving Fonseca something of an offer - but it came at a price.

"My plan after I retire from tennis is to coach [Joao] Fonseca. I'm going to be very expensive for him, so be ready," he joked.

Djokovic's response may have been tongue-in-cheek, but the Serb has been impressed with what he's seen from Fonseca so far this year.

The Brazilian teenager started his season by qualifying for his first Grand Slam main draw at the Australian Open. On his debut, he stunned No. 9 seed Andrey Rublev in straight sets.

Fonseca followed it up by winning his maiden ATP Tour title in Buenos Aires a few weeks later, and he caught Djokovic's attention.

"He's been the talk of the tour in the last several months. I mean, deservedly so," the world No. 7 said earlier this year.

"He's a very good tennis player. I mean, so young. Just incredible firepower from both ends of the baseline, serve. He's a very complete player.

"Of course, what is impressive is the way he strikes the ball, but even more so is how he handles the nerves on the court for someone that doesn't have experience at all playing at the highest level."

Djokovic may well be keen on giving Fonseca some guidance when he eventually hangs up his racket. But he's made it clear that he's still determined to keep playing.

Ahead of the US Open, the 38-year-old explained: "For me, it's really about where do I find motivation and joy? Where will I be inspired to play the best tennis? And where do I care to be, really, and play? And Slams are obviously the four main tournaments where I always feel the most motivation."

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