Former world number one Maria Sharapova has said she will fight back, after testing positive for meldonium, a banned substance, at the Australian Open. Her latest doping test results led to her provisional suspension from tennis. The Russian denies claims she missed five warnings that meldonium, which she’d been taking for a decade, was recently added to the list of banned drugs. World number five Rafael Nadal said Sharapova must pay for her negligence, and denied ever taking a banned substance to gain unfair advantage in the sport. Meanwhile men's world number one Novak Djokovic has expressed his support for her, saying he admired her courage and mature way of handling the situation.