Novak Djokovic has more soul-searching to do in order to rediscover his competitive edge on the court, according to Andy Murray's former coach Mark Petchey. The ex-reigning world number one's annus horribilis continued at Roland Garros on Wednesday (7 June) as he saw his French Open title defence unceremoniously ended by a straight-sets quarter-final defeat to Dominic Thiem.

Just 12 months ago, Djokovic capped a prestigious career Grand Slam with a memorable victory over Murray in Paris. However, he has claimed only two tour titles since then and failed to defend his respective Wimbledon and US Open crowns before a 122-week reign atop of the ATP rankings was ended in November 2016. He also split with head coach Boris Becker after three years and fell at the last hurdle in the ATP World Tour Finals.

Djokovic's struggles have continued in 2017, with victory at the Qatar Open immediately followed by a shock second-round defeat in Melbourne.

He later struggled with an elbow injury after a pair of back-to-back losses to Nick Kyrgios and parted company with the remaining members of his backroom team - longtime coach Marian Vajda, fitness trainer Gebhard Phil-Gritsch and physiotherapist Miljan Amanovic - just three weeks before the start of the French Open.

The 12-time Grand Slam champion initially showed some signs of improvement on clay and temporarily linked up with tennis legend Andre Agassi for part of the year's second major, where he beat Marcel Granollers, Joao Sousa, Diego Schwartzman and Albert Ramos-Vinolas before defending himself against accusations of tanking in a comprehensive 7-6 6-3 6-0 loss to impressive sixth seed Thiem.

Such a chastening defeat has left Djokovic considering a break from the sport and Petchey claims he has some way to go before getting back to his best form.

"It's really hard to put your finger on it," he told Sky Sports. "You think he's back to somewhere near his best and it seems like he's playing well and then, if we're being honest, the appetite for the fight just wasn't there against Thiem, which is so unlike Novak. Clearly there's still more soul-searching to do and a way to go in terms of getting himself back with the same hunger and desire in the competitive environment.

Novak Djokovic
Novak Djokovic's woes continued at Roland Garros on Wednesday ERIC FEFERBERG/AFP/Getty Images

"The margins between winning and losing are so wafer thin at this level that if you don't have this unconditional burning intensity inside of you, because winning is more important than anything else, then you don't tend to turn the matches around. That would be the thing missing from him. A lot of the times - even when he was dominating - he didn't necessarily play the best tennis but he found a way to win and recently that just hasn't been the case."

Petchey backed Djokovic to bounce back from his recent struggles, however, insisting the Serbian has "got too much of his career ahead of him for his form not to click and make it happen" and pointing to Pete Sampras winning the 2002 US Open and Roger Federer's five-year wait for an 18th Grand Slam title as evidence that normal rules do not apply to great players.