On one hand there's Ivan Lendl, whose sage advice has helped Andy Murray win two Grand Slam titles and the admiration of the British public.
On the other there's Jimmy Connors, whose ill-fated tie-up with Maria Sharapova lasted just one match before they went their separate ways.
With players increasingly turning to yesterday's stars as coaches, the question is which celebrity partnerships will live long in the memory, and which will be best forgotten.
When the Australian Open gets under way next week, there will at times be as many Grand Slam winners in the players' boxes as on the courts.
Boris Becker has ditched the commentator's microphone to guide Novak Djokovic, Stefan Edberg is working with Roger Federer and Michael Chang will advise Kei Nishikori.
France's Richard Gasquet has hired two-time Roland Garros winner Sergi Bruguera and former Wimbledon champion Goran Ivanisevic is in the corner of Marin Cilic.
In all cases, the goal is simple: winning major titles. So it is not illogical for players to turn to those with personal experience of winning Grand Slam tournaments.
Murray has blazed the trail, forging an unlikely bond with the stony-faced Lendl to end his run of four major final defeats at the 2012 US Open.
And last year, the Scot finally won over his doubters when he became Britain's first Wimbledon men's singles champion since 1936, in emotional scenes in London.
Even so, the tennis world did a collective double-take when Djokovic announced his hook-up with the flamboyant Becker, who has little coaching experience, last month.
Djokovic won last year's Australian Open and reached both the Wimbledon and US Open finals, yet apparently feels a dash of the German's vigour and adventure is just what his game needs.
Federer, striving to add to his 17 Grand Slam titles at the age of 32, has hired Edberg on a short-term basis after splitting with long-time coach Paul Annacone.
All the players and their new coaches will hope to do better than Sharapova and Connors, whose brief encounter started and ended with defeat to Sloane Stephens in the first round at Cincinnati last August.
"Jimmy came in at the wrong time and in the wrong place," Sharapova, who was badly affected with shoulder pain and did not play again last season, told the New York Times.
Sharapova starts the new campaign under seasoned coach Sven Groeneveld, while the Russian's former trainer Thomas Hogstedt is now in the camp of Caroline Wozniacki.
Both of tennis's world number ones, Rafael Nadal and Serena Williams, seek advice close to home, with Nadal backed by his uncle Toni and Williams coached by her father, along with Patrick Mouratoglou.
For those without such relatives, a celebrity coach could be the answer.
Just ask Murray, who has two wins in the past five Grand Slams, an Order of the British Empire award and was voted Britain's sports personality of the year.
"I think he's always been very honest with me. He's always told me exactly what he thought," Murray said at Wimbledon, where he embraced Lendl after his victory.
"And in tennis, it's not always that easy to do in a player/coach relationship. The player is sometimes the one in charge.
"I think sometimes coaches are not always that comfortable doing that. But he's been extremely honest with me."