Lawyers for Serbian tennis star Novak Djokovic said on Saturday that he contracted COVID-19 last month but was not experiencing symptoms and had written clearance from Australia's immigration department before traveling to the country with a medical exemption from its vaccination rules, ESPN reported. The No. 1-ranked Djokovic, who remained in immigration detention in Australia after having his visa canceled on arrival Thursday, returned his first positive coronavirus test on December 16, but 14 days later he "had not had a fever or respiratory symptoms of COVID-19 in the last 72 hours," the lawyers said in a court filing. On January 1, Djokovic received "a document from the Department of Home Affairs [that] told Mr. Djokovic that his 'responses indicate[d] that [he met] the requirements for a quarantine-free arrival into Australia,'" the documents added. Djokovic was denied entry at the Melbourne airport late Wednesday after border officials canceled his visa for failing to meet its entry requirement that all noncitizens be fully vaccinated against COVID-19. Djokovic was given a medical exemption backed by the Victoria state government and Australian Open organizers based on information he supplied to two independent medical panels. It has since emerged that the medical exemption, allowed for people who tested positive for the coronavirus in the previous six months, was deemed invalid by border authorities. Djokovic is preparing for his challenge in the Federal Circuit Court on Monday. Serbian President Aleksandar Vucic on Wednesday blasted Australia for the "maltreatment" of Djokovic with the 34-year-old having been reportedly kept alone under guard in a room at Melbourne Airport. He had also initially had his phone taken off him, reported The Telegraph. Vucic said on Instagram he spoke with Djokovic over the phone and told him that "the whole of Serbia is with him and that our authorities are undertaking all measures in order that maltreatment of the world's best tennis player ends as soon as possible". "In line with all standards of international public law, Serbia will fight for Novak Djokovic, justice and truth."