And then, slowly, over the next two-plus hours, all the way until the fifth set reached its 24th game, as the temperature dropped and the spectators' cries of "Let's go, Roger!" echoed through the shadows, everything came apart for the eight-time champion. "And I just couldn't get it done today so it's disappointing". I nearly could have.
Anderson stayed in the match thanks to his serving, compiling 28 aces.
Back to deuce. From there, it all began to change. Breaking Federer was going to be his biggest challenge, as prior to Wednesday's match the Swiss had gone 81 service games without dropping serve.
The comeback was just beginning. "Obviously I've been very pleased with the way I've played so far on the grass court season".
"I was seeing their battle between five-or-six-all to about nine-all and he's constantly under pressure, Kevin, and he was coming up with some big serves and bold tennis". But there was more.
As if Federer needed any more motivation to reclaim his Wimbledon crown next year.
That ended Federer's streak of consecutive sets won at the All England Club at 34, with the former world No 1 unable to break his own record. "I have been building over the last couple of weeks, and the level of tennis I have played in the last couple of months felt like it was getting better and better and I feel like I am peaking at the right moment".
It will be the 31-year-old's first semifinal at a Major since the 2016 French Open when he completed the career Grand Slam. He made it all the way to the US Open final in 2017. He's the top seed and playing like it, winning sets that are close and others where he's simply dominated every touch. He now has broken his opponent's serve 31 times at Wimbledon. He had brushed aside all four challengers en route to Anderson, including winning the first set of his Round 4 match against Adrian Mannarino in just 16 minutes. "You're never really safe".
So it proved, as Anderson served his way into a commanding lead during the fifth. Is it missing match points?
Anderson then served it out, ending things with a 205kph service victor, and raised both arms overhead.
"Credit to him for hanging around really that long", he added of eighth-seeded 32-year-old Anderson.
The two players then held their serves brilliantly in the fifth and decisive set, until Anderson broke Federer in the 23rd game to go up 12-11.
He said he did not believe that playing on the No. 1 Court instead of Centre Court was a factor in the defeat. Federer, an eight-time Wimbledon champion, had not lost a set here since his five-set defeat to Milos Raonic in a 2016 semifinal. Nadal will advance to play in his sixth Wimbledon semifinal, and his first since losing in the finals in 2011. Novak Djokovic is generally very nice and Serena Williams is great too but the ball boys and girls have to be on their toes with her.
The 12-time Slam victor prevailed despite picking up two code violations and accusing umpire Carlos Ramos of "double standards".
He then let rip at Ramos for failing to sanction Nishikori for a similar act in the fourth set.