Novak Djokovic has been a professional tennis player for over two decades.
The Serbian has seen plenty of players come and go from the tour, including his greatest rivals Roger Federer and Rafael Nadal who have now retired.
Over such a long period of time, there will inevitably be aspects of the game that will change and develop.
While he tries to win a seventh Miami Open title, Djokovic opened up on one of the biggest changes he has identified in tennis since he started his career.

Novak Djokovic says a change in tennis helped Gael Monfils and Grigor Dimitrov
Novak Djokovic is now into his late thirties and is one of the oldest players on the ATP Tour.
Some of the 24-time Grand Slam champion’s fellow veterans on the circuit are Gael Monfils, 38, and Grigor Dimitrov, 33.
Despite being deep into their thirties, both players are still playing some excellent tennis and produced some strong performances across the North American hard court swing.
Djokovic thinks the advances in fitness and recovery since he arrived on tour has helped the likes of himself, Monfils and Dimitrov to still be playing such a high level of tennis. “Monfils, myself, Grigor. The veterans of the game are showing we can still play at a high level,” Djokovic told reporters in Miami.

“It’s so nice to see both Grigor and Gael physically being able to maintain that level of competition and stay with the young guns who are hungry and fit and tough.
“I think the level of fitness and recovery and overall approach to the work from both physical and mental side has improved so much in our game, compared to the time I was breaking through in the professional game.
“I don’t recall it being so professional as nowadays, pretty much every player in the top 30 in the world has a full team of three or four people around and takes care of them and their body and that reflects on the court.
“I think that’s why careers are extended now. 25 years ago, it was if you hit your 30’s, start counting your days, but nowadays I think it’s until at least 35. Maybe even more. I am in that group, not getting any younger, but I still feel good about my body and my tennis.”

Could Novak Djokovic play Grigor Dimitrov at the Miami Open?
Monfils is now out of the Miami Open after suffering a three-set defeat to Sebastian Korda.
The American will face Djokovic in the quarter-finals, and he will try to defeat the former World number one for the first time.
Dimitrov is into the last eight and will take on Francisco Cerundolo, who is coming off back-to-back wins against home favourite Tommy Paul and Casper Ruud.
Should Djokovic and Dimitrov win their respective quarter-final matchups, they will play one another in the semi-finals.
This would be their 14th career meeting, and Dimitrov has claimed just one victory.
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