Instead, it's the South African who is into his first Wimbledon semifinal after a 2-6, 6-7 (5), 7-5, 6-4, 13-11 marathon win.
Anderson staved off Federer's first and only attempt at match point, trailing 5-4 in the third set, before winning the game to tie the set at 5-5 and ultimately winning the next game to take a 6-5 lead. About Anderson, Federer said: "He's got a nice, big serve that he can rely heavily on".
The Swiss superstar started off proceedings and held serve as did Anderson a game later.
Federer was rattled, but the credit belonged to Anderson, who had disrupted his illustrious opponent's serve. The match was a minute shy of three-and-a-half hours, so his physical condition will certainly be tested against the fresher Federer, but he's certainly not lacking confidence. It rattled Federer, who blew the next match point and then double faulted on break point.
"I really hope it´s an example of sticking to your dreams and keep believing in yourself".
The only other times that Federer has surrendered a two-set lead came against Lleyton Hewitt in Switzerland's 2003 Davis Cup semifinal loss to Australia in Melbourne, to David Nalbandian in the 2005 Masters Cup decider and to Jo-Wilfried Tsonga and Novak Djokovic at consecutive slams at Wimbledon and the US Open in 2011.
While top seed Federer was only at his scintillating best in the first set, nothing could be taken away from Anderson.
"I feel like a lot of aspects of my game can give him a lot of trouble", Anderson said.
The 36-year-old had needed only 26 minutes to take the first set, leaving him horrified as a fifth successive Wimbledon semi-final slipped through his fingers from such a commanding position. He extended it to 34 against Anderson, but then the wheels began to come off.
Djokovic defeated 24 seed Kei Nishikori in four sets on Wednesday at Wimbledon, 6-3, 3-6, 6-2, 6-2, to advance.
"It's one of those average days you have to try to win the match", said Federer, referring to his own level of play. After making it to the fourth round of the Australian Open, an event where he's dominated historically, Djokovic lost in the first round of several masters events, including the Indian Wells Masters and the Miami Open. At 33 years old, he'd taken just one of the previous 18 Slams and the chorus of questions about whether he'd ever win another seemed to be reaching its crescendo.
Soon enough, Djokovic was on his way to the semi-finals, where he will meet Rafael Nadal. I'm very pleased to get through.
Del Potro said: 'I think I will be in good condition.
"I was playing tennis".