Novak Djokovic's latest bid for a record 25th Grand Slam title crashed to a halt on Friday as 28th-ranked Alexei Popyrin knocked the defending champion out of the US Open third round.Popyrin handed Djokovic his earliest US Open exit in 18 years and his earliest Grand Slam exit since he fell in the second round of the Australian Open in 2017 — which was also the last year the Serbian great failed to claim a single Grand Slam title.