Kevin Anderson did the unthinkable on Wednesday, rallying from two sets down against the always great Roger Federer in a grueling Wimbledon quarterfinal match to advance to his first semifinal. After a marathon final set, a double fault on Federer in the 23rd game was ultimately what did in the No. 1 player. 

Federer's first double fault of the match was perhaps the most costly error either player made. Anderson took the match 2-6, 6-7, 7-6, 6-4, 13-11. Federer broke Anderson's serve three times, but never did so after the second set.

Federer, meanwhile, had his serve broken four times after not having it broken in any of his previous matches during this Wimbledon run. His record of 34 straight Wimbledon wins when up 2-0 was also snapped, and Anderson forced him to a fourth set for the first time at Wimbledon since Federer played Milos Raonic in 2016. Federer is now 266-3 when leading 2-0.

Anderson, who is now 32, has stormed onto the scene in the past 10 months. He made it to the the US Open final last year, and he's firmly established himself as a top-10 player. Federer ended up with more points won than Anderson in this match, but ultimately the difference came down to two unforced errors. Federer had 33, 14 of which came in the fifth set, while Anderson finished with 31.

"Down two sets to love I just tried my best to keep fighting and scraped through the third and fourth set," Anderson said after the match, per Wimbledon's website. "By the end I thought I did a great job. Beating Roger Federer at Wimbledon is one I will remember. I just kept telling myself this will be my day."

It took four hours and 13 minutes, but it did indeed become Anderson's day.

Elsewhere in the men's bracket, Rafael Nadal rounded out the day with a fantastically played match against Juan Martin del Potro, who came up just short of his second Wimbledon semifinal. Nadal had a tough time with Martin del Potro, needing five sets to beat him, but his service game was just enough to get by 7-6, 6-7, 4-6, 6-4, 6-4. Games 6 and 8 in the final set were the defining ones. Del Potro had opportunities in both to break Nadal's serve, and both went on for over nine minutes, but Nadal persevered to stave del Potro off from tying the set.

It took nearly five hours for the match to go final, somehow longer than Anderson's day with Federer. Nadal will advance to play in his sixth Wimbledon semifinal, and his first since losing in the finals in 2011.

Anderson's next opponent will come Friday against No. 9 seed John Isner, who made his first Grand Slam semifinal with a win over Milos Raonic. Raonic found himself hobbled in the fourth set, with Isner prevailing 6-7, 7-6, 6-4, 6-3. Before this tournament, Isner had made the quarterfinals of a Grand Slam only once before -- in 2011's US Open. He knocked on the door by making it to the French Open's fourth round, and he now seeks out his first Grand Slam title.

Isner rallied behind a dominant first serve, converting 73 percent of them and winning those serves at an 80 percent clip. Raonic never broke Isner's serve, and while Isner broke Raonic's serve just three times, it was just enough to move on.

Novak Djokovic, Nadal's one-time archrival, has had a lot of ups and downs over the past few years, but he's back in the semifinal to face off against Nadal. Djokovic defeated 24 seed Kei Nishikori in four sets on Wednesday at Wimbledon, 6-3, 3-6, 6-2, 6-2, to advance.

Djokovic has improved in every tournament in 2018, making it to the fourth round of the Australian Open, the quarterfinal round of the French Open and now the semifinal round at Wimbledon. Djokovic last appeared in the semifinals at Wimbledon in 2015, when he won. His last semifinal appearance at a Grand Slam was at the US Open in 2016, where he lost in the final to Stan Wawrinka.

Djokovic missed the end of the 2017 season after lackluster (for him) performances in the first three majors of the season due to an elbow injury. Since then, it has been a long rehabilitation process. 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. It wasn't until the Italian Open in May that he seemed to find his form again, ultimately losing in the semifinals to Rafael Nadal in the semifinals. Since then, he's been far more consistent, making it to the quarterfinals of the French Open and the finals of the Queen's Club Championships.

This, however, is already the high point of Djokovic's year, and he knows it. "It feels great to be in the last four," Djokovic said, via Wimbledon's Twitter account. "I feel like I'm peaking at the right moment."

He's playing like it, at least. Djokovic broke Nishikori's serve seven times, and finished with six aces. He now has broken his opponent's serve 31 times at Wimbledon. He'll need to keep up that consistency, but at this point he's eyeing his fourth career Wimbledon title and 13th Grand Slam.