"Coach" may not be the right title. What elite tennis pros seek, in those whom they hire (and fire) to further their success, is something closer to a shrink, a valet, a person to offer aid and comfort as much as technical know-how.
At the U.S. Open stage, players already know how to play. So a coach, 18-time major-tournament champion Chris Evert said, "is like a therapist, a baby-sitter. It's an emotional as well as a physical job."
Furthermore, after a few years with the same coach, "You start to feel a little stale," Evert said. "Sometimes you need some new inspiration, a new point of view, some new blood."
Roger Federer, coachless for many years while winning Grand Slam events, employed Paul Annacone and won some more. Andy Murray famously turned to Ivan Lendl -- who, like Murray, had lost his first four major finals -- and quickly won his first.
Four-time major-tournament champion Maria Sharapova famously signed up old champion Jimmy Connors after her early exit from last month's Wimbledon. Then pink-slipped him exactly one match later.
Just since Wimbledon, four others among the sport's most accomplished women have changed coaches: former U.S. Open champ Samantha Stosur, former No. 1 Ana Ivanovic, former French Open winner Francesca Schiavone, rising British star and Laura Robson.
The only move that truly mystified tennis insiders was the Sharapova-Connors arrangement, brief as it was. "I wonder what Maria thought she needed Jimmy for," said Cliff Drysdale, the television commentator and former tour professional. "Jimmy is not a coach, and one of the questions is why he'd want to?
"The job of a coach is wide-ranging," Drysdale said. "Arrange for massages, arrange for ball people, so many things. It's not as simple as being in the stands and nodding your head."
Still, coaching change clearly is normal procedure. Li Na, the year after she won the 2011 French Open, replaced her husband, Jiang Shan, with veteran Argentine coach Carlos Rodriguez, a move she said helped her tennis and saved her marriage.
"If husband's the coach," she said, "I have to listen to what he say, but I didn't want to listen to what he say on the court. Now, if he say something, I say, 'You're not coach. I just listen to what coach say.' "
Before her third-round victory Friday over Robson, who knocked Li out of last year's Open in the same round, Li said she went to Gonzalez "to help me speak out and put pressure out. After the talk, I was feeling much, much better."
In 1983, Martina Navratilova -- who already had won six of her eventual 18 Slam titles -- fired coach Renee Richards the day after Navratilova was upset in the fourth round of the French Open. Two weeks later, she hired Mike Estep, telling him she wanted to be "the greatest player ever."
Andy Roddick, in a 13-year career that ended last year, worked with Brad Gilbert, then Connors, then Larry Stefanki as coach.
"It's kind of funny," said Coco Vandeweghe, who just fired her coach before losing her first-round match at the Open. "Because you employ these people but they tell you what to do. It's kind of a weird situation."
A 21-year-old Californian whose career ranking has plunged from a high of 69 last summer to her current 191, Vandeweghe parted with former tour pro Jan-Michael Gambrill. Interviews for the position will commence soon.
"In my eyes," Vandeweghe said, "a coach is there to support you and drive you on days where you really don't want to work as hard as you can . . . make sure you're not tired, overtraining, also scout opponents. They're supposed to encompass all of that and also be a rock for you as well."
The more accomplished the player, of course, the more financial able he or she is to hit the new-coach re-set button in constantly foraging for a competitive edge. "It's like getting a new racket," Drysdale said. "It's sort of inspiring.
"I think a coaching change, sometimes even for the sake of change itself, is a good thing for players."
In such an individual sport, coaches provide a you-are-not-alone underpinning. And, when things don't work out, they can be handy fall guys.