Simona Halep competes at the 2022 US Open. (Robert Prange/Getty Images)

Simona Halep’s former coach, Darren Cahill, came to her defense on Sunday after the two-time Grand Slam winner tested positive for a banned substance.

The two worked together for six years before parting ways. Halep recently transitioned to work with Patrick Mouratoglou, who famously coached Serena Williams.

In his statement, Cahill said there is “NO chance” Halep “knowingly or purposely” took a banned substance at the US Open, as the International Tennis Integrity Agency said in a statement on Friday.

“She is an athlete that stressed about anything prescribed to her by a medical professional, or any supplement that she used or considered,” he wrote, adding that she often double- or triple-checked to ensure that her medications were legal and she would not take a substance if it were questionable.

Both he and Halep “believe in the ITIA testing program,” Cahill wrote, adding that Halep submitted to tests “without complaint.”

“Competing against clean athletes was important to her,” he continued.

Halep tested positive for roxadustat, a banned substance, at the US Open in August. Calling it the “biggest shock of her life,” Halep said in a statement that she will continue to fight “to prove that I never knowingly took any prohibited substance.”

The ITIA, which conducts the drug tests, said in a statement that Halep requested a second sample be tested after the first came back positive. That result confirmed the finding of the A sample.

As a result, Halep is unable to compete. The 31-year-old Romanian star, currently ranked No. 9 in the world, last won a Grand Slam at Wimbledon in 2019.

“Simona’s integrity is faultless, she respects her peers, she loves the game and she always has her feet firmly planted on the ground as a humble, approachable champion,” Cahill wrote. “Honesty has always been her greatest strength and her biggest weakness. We would often laugh about the fact that she can’t act and can’t tell a little white lie.

“Due process will now follow to reveal answers to many questions.”