Serbian tennis great Novak Djokovic on Monday set a record for most weeks at No. 1 in the 48-year history of the ATP rankings. Djokovic entered his 311th week at the top of the rankings, one week longer than Swiss 20-time Grand Slam winner Roger Federer's record.18-time Grand Slam champion Djokovic grabbed his ninth Australian Open title last month. Federer had set the record in July 2012, surpassing American Pete Sampras' record of 286 weeks.Djokovic, 33, had fallen to No. 22 in May 2018 amid a series of injuries and downturn in form. However, he stormed back into the top five after winning Wimbledon and the US Open in 2018 and following that up with a win at the 2019 Australian Open and 2019 Wimbledon.Federer, Djokovic and Spain's Rafael Nadal have dominated men's singles tennis, particularly the Grand Slams, for nearly two decades.From the 2003 Wimbledon to the 2021 Australian Open, the three players have won 58 out of 70 Grand Slams. They won 18 consecutive slams from the 2005 French Open to Wimbledon in 2009, and 13 consecutive slams from the 2017 Australian Open to the 2020 Australian Open.