Simona Halep crashed out of Roland Garros in the second round, but coach Patrick Mouratoglou says he must take 'full responsibility' for it.
Halep lost out to teenager Zheng Qinwen 2-6, 6-2, 6-1, although she was leading before she suffered a panic attack on court.
The defeat leaves Halep still searching for her best form and battling to cling onto her top 20 ranking ahead of the grass season.
"I’ve always been proud of my successes with my players, but then I also have to acknowledge when I’m not doing a good enough job," Mouratoglou wrote on Instagram.
"The results we’ve had the past month in Madrid, Rome and Roland-Garros are insufficient for someone of Simona Halep's caliber and I take full responsibility for them.
"She is fully dedicated, motivated, gives it everything on every ball. She is a champion - her track record speaks for itself.
"I expect much better from myself and I want to extend my apologies to her fans who have always been so supportive."
Simona Halep was looking in fine shape until the panic attack struck her.
The former Roland Garros and Wimbledon champion called the doctor onto court to help before battling on, but she was unable to prevent it from contributing to her defeat.
“I didn’t expect [it] because it was just a panic attack," Halep said afterwards. "It happened.
“I didn’t know how to handle it, because I don’t have it often. Yeah, I don’t really know why it happened, because I was leading the match. I was playing well.
“But it just happened and I lost it. I couldn’t focus. After the match it was pretty tough. But now I’m good. I’m recovered and I will learn from this episode.
“It was nothing like dangerous, in my opinion, but it happened. So it’s good that now I can smile.”
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