Novak Djokovic remains the men's world number one, but the Serbian has endured a slow start to the 2024 campaign, and he is 11/10 to not win a Grand Slam before the end of the year.
Djokovic has yet to win a title from his first three outings this year, and he has already changed his team in an attempt to bounce back with three Grand Slams still up for grabs.
The 36-year-old reached the semi-finals of the Australian Open in Melbourne in January, but he fell short against Jannik Sinner, who went on to win the title Down Under.
Djokovic's last success came at the ATP Finals in November, when he defeated Holger Rune, Hubert Hurkacz and Sinner.
After taking a short break, Djokovic has been unable to maintain those lofty standards, but he has only featured in three tournaments since the start of the new season.
The world number one decided to change his coaching team last month ahead of the clay court campaign, announcing his split with coach Goran Ivanisevic.
The former Wimbledon champion had been Djokovic's main coach since 2022, while he also worked alongside his former mentor, Marian Vajda, since 2018.
Djokovic has won 24 Grand Slam titles so far in his career and with the Serbian into the twilight years, he quickly decided to change his approach going into a busy period of the season.
Confirming his decision, Djokovic wrote on Instagram: "Goran and I decided to stop working together a few days ago.
"Our on-court chemistry had its ups and downs, but our friendship was always rock solid."
Ivanisevic was nominated for ATP Coach of the Year in 2023, having helped Djokovic win three of the four Grand Slam titles, but Djokovic is now on the lookout for a new coach ahead of the French Open, where he is 9/4 to win the title.
Djokovic has already made the bold move to change his team, and he has admitted that he needs to to balance his "private and professional schedule" having withdrawn from the Miami Open earlier this year.
He was surprisingly beaten by Italian world number 123 Luca Nardi at Indian Wells, but it will take a brave person to write off the world number one.
Djokovic admitted last May that he had struggled to find his rhythm, yet he finished the year with seven titles and won £15m in prize money.
While he has already missed out on the Calendar Grand Slam, he is still chasing a coveted 25th Grand Slam, which would mean he is no longer sharing the record for major success with Margaret Court.
Djokovic has been through his fair share of adversity in the past, both on and off the court, but he has always responded, and he is priced at 25/1 to win the three remaining Grand Slam titles, 9/2 to win two and 5/4 to win one.
Djokovic will always be remembered for his achievements on the tennis court, and his rivalries with Rafael Nadal, Roger Federer and Andy Murray will live long in the memory.
However, at 36, the Serbian is now having to keep up with the younger generation, and he and Nadal are now the elder statesmen.
Sinner has made a remarkable start to the 2024 season, and he has the chance to become world number one if he can enjoy a successful clay-court season.
Spain's Carlos Alcaraz will also be in the mix on his favourite surface, but wrestling the world number spot from Djokovic will be no mean feat.
He has ruled at the top for 419 weeks and will break Roger Federer's mark of the oldest world number one in history next week.
Eventually, Djokovic will have to move over for the new kids on the block, and it promises to be a fascinating 12 months as the Serbian tries to prove he is capable of winning either on his own or with a new coach.
Alcaraz is 11/4 to win two Grand Slams, while Sinner is 6/4 to get his hands on a second major trophy.