Novak Djokovic has achieved another milestone in his illustrious tennis career, equaling Steffi Graf to spend the most weeks at No. 1 in the world. On Monday, Djokovic started his 377th week as the Association of Tennis Professionals (ATP) world No. 1, spending the most weeks in that spot since the ATP ranking system began in 1973. The feat matches him with the Women’s Tennis Association (WTA) leader, Graf, who also held the top spot for 377 weeks in her career. The most weeks at No. 1: Djokovic 377 Graf 377 Martina Navratilova 332 Serena Williams 319 Roger Federer 310 #djokovic #atp #goat #australiaopen (📷 Lintao Zhang/Getty Images)