Milos Raonic has called for a review into tennis scheduling after an injury-plagued year got even worse at the Japan Open.
Roger Federer and Rafael Nadal have been the story of 2017, returning to the top of the rankings after splitting the four grand slams between them - Federer won the Australian Open and Wimbledon, Nadal the French and US Opens.
But their incredible resurgence has been met with little resistance from the likes of Andy Murray, Novak Djokovic and Raonic -
the top three players in the rankings at the start of the year.
Raonic returned to the ATP Tour on Wednesday in his first tournament following a seven-week absence with left-wrist surgery, but was forced to retire from his second round clash against local favourite Yuichi Sugita.
The Canadian lasted just eight minutes before he was forced to call for the trainer in the very first game, clutching his right calf.
He eventually threw in the towel, withdrawing from his sixth event of the year.
It's a bitter blow for Raonic, who on Tuesday suggested the ATP needed to look at changing its gruelling schedule.
"It's been very frustrating," said Raonic, who started this year at No.3 but has slipped to No.12 in the rankings.
"I think I've had more than a dozen different injuries and reasons that have kept me away from tournaments. That hasn't been fun because I haven't been able to focus on tennis, I've been focusing on 'Can I play today or can't I?' rather than, 'What do I need to do with my tennis game?"'
Raonic knows tennis isn't a sport that's easy on the body, and the travel and length of the season are demanding, too.
"I believe out of those of us that finished top five last year, I'm the only guy still trying to play this year, and none of the top five played the US Open," Raonic said.
"Maybe it's testament to some kind of reform being needed for the sake of players' careers, and being able to provide a certain calibre of tennis for spectators.
"Scheduling, the length of the year and how spread out - geographically and throughout the year - the tournaments are, especially the top tournaments for the top players, is something that deserves a second look. It's hard to peak four times of the year for grand slams, let alone for other tournaments."
The length of the season has long been an issue for players, something the men's and women's tours have taken some steps to address.
Even the biggest stars on the men's tour, Federer and Nadal, had injury layoffs before returning to win two major titles each this season.
Big guns Murray, Djokovic, Stan Wawrinka and Kei Nishikori have all had their years curtailed by injury, aiding Federer and Nadal's rapid rise up the rankings.
Nadal returned to top spot for the first time since 2011 in the lead-up to the US Open, and cemented it with victory at Flushing Meadows.
However he didn't face a single opponent in the top 25 on his way to the title, the first time that's happened since 1998.