Kei Nishikori, the former World No. 4, announced his retirement from professional tennis at the age of 36, citing ongoing injuries and anxiety as key factors. Nishikori, who began his professional career in 2007, made history as the first Japanese player to break into the top 10 and achieved a career-high ranking of four. He also won 12 ATP Tour titles and earned a bronze medal at the 2016 Olympics in Rio. Following his announcement, Naomi Osaka took to social media to honor Nishikori, calling him 'the best' and expressing her admiration for his career. In her heartfelt message, Osaka reflected on how Nishikori inspired her during her youth and expressed hope that they could play doubles together in the future. She described him as a 'big kid' with a positive personality, highlighting the close relationship they share as fellow Japanese tennis players.