Novak Djokovic sees all of the injuries to top men at the Australian Open and draws a direct connection to the two-week quarantines that players went through because of the coronavirus pandemic when they arrived in the country last month. Djokovic says players don’t want to have to keep quarantining and he raised the possibility of an NBA-style “bubble.” Djokovic himself has been dealing with an abdominal muscle problem. So was the guy he beat in the quarterfinals. The player Djokovic will face in the semifinals advanced by eliminating someone whose back spasms were so bad he had a hard time putting on his socks.