No matter how much work is done on the practice court, how much tactical input is given, how many motivational words are said, a tennis coach is simply powerless if their player self-destructs in front of their eyes.
That was the case at Wimbledon on Thursday as Carlos Rodriguez watched Chinese Li Na go walkabout in the second set before pulling herself together to beat Romanian Simona Halep 6-2 1-6 6-0 on a sun-bathed Court Two.
The sixth seed, China's first grand slam champion when she triumphed at the French Open in 2011, eased through the opening set but after sitting idle in her seat while Halep received treatment to her back, she fell apart.
As each error flew off the strings of 31-year-old Li's racket, Argentine Rodriguez, the man responsible for steering Belgian Justin Henin to number one in the world, sank a little deeper into his seat, a look of resignation on his face.
"She didn't manage that time in the right way," Rodriguez told reporters, when asked by reporters at courtside if the stoppage had caused the meltdown that threatened to see another high-profile seed tumble out of the championships.
"She lost her adrenaline. Li helped her opponent a lot to come back into the match. We have to continue to work on it. She has to be able to manage that.
"She went out of the match a little bit but I'm happy that she recovered to produce some good tennis."
He said being a coach was as much about psychology as the mechanics of the strokes.
"It all depends on her really. I'm happy but there's a lot of work to be done. There were two different players there today in the first and the third sets compared to the second," added Rodriguez who scribbled notes during the match.
"I'll let her talk to me about the second set. She had the problem, I don't know. For me it's unacceptable.
"It's about her personality. She couldn't accept that she wasn't ready to play (after the break). She put the head down and then took half an hour to get going again.
"She was fighting with herself, instead of her opponent."
"She's an unbelievably nice human being and that's what upset me a lot, that's what upsets me," he shrugged.
"When I see that animal in there on a daily basis I say to her, "How can you do that to yourself".
"I say to her I just want to help you."
Li began working with Rodriguez last year after being coached by her husband Jiang Shan, who now performs the role of hitting partner.
The post-match conversation between Li and Rodriguez would have been an interesting one.
"I still didn't talk to Carlos because I think he went to see the next opponent," Li, who will have to be on her mettle against 32nd seeded Czech Klara Zakopalova in round three, said in a news conference.
"When I see him I will say, "Please kill me right now!".
"I don't know what happened in the second set."
The match was a curious, topsy turvy affair, with Li finishing how she started.
"Welcome to the crazy women's tennis tour," she said.
"I lose my concentration and she kicked my arse in the second set, but I woke up.
"This has been the worst Wimbledon, for so many big stars going out. I was sad, but at the same time I really didn't want to be the next one."