also of Spain in the second round 6-3, 7-6(8-6) before also upsetting the top ranked American, the 13th seeded John Isner 6-3, 6-4 in third round.
In the second round, Simon also recorded an upset as he defeated the fourth seeded Stan Wawrinka of Switzerland 5-7, 7-5, 6-4.
Head to head the 33 year old Federer leads the 27 year old Djokovic 18-17. However Djokovic won the duos’ last meeting in the final of Wimbledon 6-7(7-9), 6-4, 7-6(7-4), 5-7, 6-4.
Federer is a seven time Wimbledon champion; last winning in 2012.
Djokovic took his first of two Wimbledon titles in 2011.
This year Federer and Djokovic split their matches played 2-2 and their upcoming matchup could be another instant classic.
“Roger is one of the best players ever in the game,” said Djokovic. “There is no clear favourite. I think every time we play against each other, it’s a thriller. It's really a big challenge for both of us. We need to bring our A game in order to win.”
Win or lose, on Monday, Federer will overtake Nadal as the world number two in the ATP Tour rankings.