SYDNEY, Australia -- Darren Cahill, a renowned coach who helped Simona Halep to Grand Slam glory, said Monday there was "no chance, none, zero," that the former world number one purposely took drugs.

The Romanian was provisionally suspended at the weekend for taking the banned substance roxadustat after she provided a sample at the US Open.

Halep insisted she would "fight until the end" to prove her innocence with the result "the biggest shock of my life".

The 2018 French Open and 2019 Wimbledon champion is the highest-profile player to fail a drugs test since Maria Sharapova in 2016.

Australian Cahill, who guided Halep to world number one in 2017 and her Roland Garros crown in a six-year alliance, leapt to her defense in a lengthy Instagram post.

"Firstly, and most importantly, there is NO chance Simona knowingly or purposely took any substance on the banned list. None. Zero," he wrote.

"She is an athlete that stressed about anything prescribed to her by a medical professional (which was rarely), or about any supplement that she used or considered.

"Simona wore out the words 'please double check this, triple check this to make sure it's legal, safe and permitted. If you are not sure, I'm not taking it'."

He said they both strongly believed in the International Tennis Integrity Agency (ITIA) testing program and would often discuss the number of times she was tested.

"She did it without complaint, with the reassurance of knowing other athletes were being tested just as frequently.

"Competing against clean athletes was important to her. It's important to everyone and while the system is not perfect, it works."

He added that her integrity was "faultless", ending: "I stand with Simo."

The ITIA, which oversees tennis' anti-doping programme, said it had informed her on October 7 of her provisional suspension.

It said Halep had exercised her right to have her 'B' sample analysed, which confirmed the presence of roxadustat.

© Agence France-Presse