Roger Federer has made a return to Wimbledon — but to watch, not play, tennis. The eight-time champion at the All England Club sat in the Royal Box during his former rival Novak Djokovic's four-set victory over Alex de Minaur in the fourth round Monday.

The win marked the 16th time Djokovic has moved into the quarterfinals at Wimbledon. The event has been his second-best Grand Slam over his career. Djokovic has seven wins at Wimbledon, and has played in the final at the event in each of the last six Wimbledons.

After surviving a tough match against Alex De Minaur in the fourth round at Wimbledon, Novak Djokovic had a funny reason why Monday's win meant more to him.