It is that time of the tennis season: One year is now largely put to bed—give or take some fun and games in the IPTL—and preparations are under way for he new. And a key element in that preparation is often a review of the players’ coaching set-ups.

Within a matter of weeks, numerous announcements have surfaced, and not just from players struggling with form. Many are men and women enjoying career-high rankings and a year of unprecedented success.

Madison Keys, ranked No8 and fresh from her first WTA Finals in Singapore this year, reached the final of two of the tour’s most prestigious tournaments, Rome and Montreal, plus the semis at the Rio Olympics and Beijing. She also won in Birmingham. But she has jumped ship from Thomas Hogstedt, who has worked with the likes of Maria Sharapova, Li Na and Caroline Wozniacki, after just eight months together.

No6 Karolina Pliskova announced, immediately after reaching her first WTA Finals and winning the Fed Cup, that she was parting from Jiri Vanek, who has resided over a surge in the Czech woman’s form this year. Pliskova reached her first Premier Mandatory semi in Indian Wells, won her first Premier in Cincinnati, and made her first Major final at the US Open.

Not that coaches with such a good curriculum vitae hang around for long: compatriot Petra Kvitova has taken on Vanek, after she parted ways with her coach of seven years, David Kotyza, at the start of the year. Interim trials with Frantisek Cermak and Wim Fissette did not last, but Cermak has been snapped up by another Czech, Lucie Safarova.

Two more coaching arrangements announced within a day of each other have caused particular surprise.

Johanna Konta’s 2015 breakthrough from a ranking around 100 before her run to the fourth round of the US Open to a career-high No10 has come under the guidance of Esteban Carril. But she is moving into the 2017 season without him, and with little comment thus far about her intentions.

It is a surprise because the last year two years have seen the maturation of Konta into a confident, calm woman who has beaten the likes of top-five players Garbine Muguruza, Simona Halep and Dominika Cibulkova, reached the semi-final of the Australian Open, won her first title at Stanford, and made the finals of one of the biggest events in the calendar, the Beijing Premier. Such has been her rise that she claimed the WTA’s Most Improved Player Award only a month ago, after becoming the first British woman to break the top 10 since 1984.

The other surprise comes from the top of the men’s game, new world No3 Milos Raonic, who announced his parting from Carlos Moya after just one season together. And it has been some season: A first Australian Open semi-final, a first Major final at Wimbledon, and the semis at the World Tour Finals. Credit for some of that success also goes to John McEnroe, consultant coach in the grass season, and a tie-up that improved the Canadian’s front-of-court game.

But if there has been a high turnover of former players in Raonic’s box, he has ensured one constant with Riccardo Piatti, with whom he began working exactly three years ago.

In contrast with all this jostling, the new world No1, Andy Murray, seems to have found the winning formula.

One of the first to take on the now-familiar ‘super-coach’ in Ivan Lendl, his choice quickly produced results: Olympic gold, the US Open and Wimbledon titles.

That partnership ended when Lendl took time out for other projects, and Murray again broke the mould by appointing a former women’s champion, Amelie Mauresmo in 2014. He then slotted Jonas Bjorkman into the team for a few months during Mauresmo’s maternity leave, but with Mauresmo unable to continue her full-time commitment to Murray, the Briton recruited friend Jamie Delgado at the start of this year.

Now with a close-knit, stable group around him, Murray delivered his piece de resistance: He attracted Lendl back to his box after the French Open.

He went on to have the most successful six-month stretch of his career with what now looks like the most gelled package of complementary strengths on the tour. Murray has never looked happier or healthier, nor ever played so well: And he has even got Lendl smiling.

Murray has, however, remained courteously silent about the movements of former team-member, Dani Vallverdu, who moved to Tomas Berdych’s box in 2014—but for only 18 months.

The Czech saw his chance to snap up Marin Cilic’s coach, Goran Ivanisevic, during this year’s US Open Series, revealing something of the ruthless decision-making required in the fast-changing scenery of pro tennis:

“My results lately have not been what I expected. As I am not a tennis player at the beginning of his career, I have to act quickly when I feel that I need a change.”

The big Croat, a former Wimbledon champion, had worked with compatriot Cilic for almost three years, guiding him to the US Open title in 2014. Cilic then recruited Bjorkman, and immediately won his first Masters in Cincinnati and has ended the year at a career-high No6.

As the eloquent Joni Mitchell sang: “And the seasons they go round and round, And the painted ponies go up and down…”

And the merry-go-round of players and coaches will run and run…

More coaching questions for 2017

What of Vallverdu, then? After a very brief spell with Juan Martin del Potro in the grass season, he tied up with Grigor Dimitrov at the Toronto Masters. Dimitrov gets through coaches faster than most, and Vallverdu followed less than a year’s residency with Franco Davin—who has been long-term coach to del Potro. The big Argentine still seeks a permanent replacement.

Borna Coric, who began working with Miles Maclagan just a year ago, has already moved on: He has announced that he will work with Ivica Ancic, brother and former coach to Mario Ancic. The 20-year-old fellow Croat reached his first two finals in 2016 before being sidelined by knee surgery in September.

David Goffin, who started 2016 ranked No16 and ended the year at a career-high No11, has ended his partnership with coaching consultant, Thomas Johansson, despite back-to-back semi-final runs at Indian Wells and Miami and a first Major quarter-final at Roland Garros. Goffin will continue to work with regular coach, Thierry Van Cleemput.

Elina Svitolina, after reaching a career-high No14 this season, has parted from Iain Hughes after two and a half years. The 22-year-old Ukrainian has been working with Justine Henin as a consultant coach, but there is currently no news on Svitolina’s 2017 set-up.