Novak Djokovic’s quest for a record 25th grand slam title has been cut short at the Australian Open after he stunningly retired from his semifinal match due to a left leg injury.

Novak Djokovic has reacted to the crowd at the Australian Open booing after he decided to retire from his semifinal against Alexander Zverev. The Serbian tennis player, 37, had taken to the court with his left leg heavily taped following Tuesday’s injury.

When it comes to effort on the tennis court, few players can compare to the legendary Jimmy Connors. The eight-time Grand Slam champion built a reputation for being one of the most hard-working players on the ATP Tour.