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 association with Maria Sharapova lasted just one match before they went their separate ways.
With today's players increasingly turning to yesterday's stars as coaches, which celebrity partnerships will live long in the memory and which will be best forgotten?
At the Australian Open, 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 Marin Cilic's corner.
In all cases, the goal is simple: winning major titles. So it is not illogical for players to turn to those who have personally experienced what it's like to win Grand Slam tournaments.
Murray 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.
Even so, the tennis world did a collective double-take last month when Djokovic announced his hook-up with the flamboyant Becker, who has little coaching experience,.
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 vigor 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 longtime 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 the Russian's loss to Sloane Stephens in the first round at Cincinnati last August.
"Jimmy came in at the wrong time and in the wrong place," said Sharapova, who was badly affected by shoulder pain and did not play again last season.
Sharapova starts the new campaign under seasoned coach Sven Groeneveld, while her former trainer, Thomas Hogstedt, is now in the camp of Caroline Wozniacki.
Meanwhile, the world's No 1 male and female players seek advice closer to home.
Rafael Nadal is coached by his uncle Tony, while Serena Williams is coached by her father, along with Patrick Mouratoglou.
For those without family members qualified to step up, 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 Ivan's always been very honest with me; he always says what he thinks," Murray said at Wimbledon, where he embraced Lendl after his historic triumph.
"And in tennis, it's not always that easy to do in a player/coach relationship.
"The player is sometimes the one in charge, and I think sometimes coaches are not always comfortable in that position. But he's been extremely honest with me."
(China Daily 01/14/2014 page24)