The contrast in experience and accomplishments is striking.
Federer, 32, owns 17 major titles and will be playing in his 35th career Slam semifinal.
Djokovic, 27, has won six majors. This is his 23rd such semifinal.
Raonic and Dimitrov are both 23 and making their debuts at this stage of a major.
"You can't really outrun time, in one way. New guys got to come up and they've got to step up. We've been doing better and better, especially throughout this year," Raonic said about the prospect of a transition at the top of the sport.
"It's good to be a part of it," he continued. "It's nice to see that sort of human side to those four guys."
Here are some things to watch Friday at Wimbledon in the men's semifinals:
Federer • A year after exiting in the second round while bothered by a bad back, Federer is again playing dominating grass-court tennis. Since winning his first Grand Slam title at Wimbledon in 2003, though, Federer has never gone this long without reaching a major final it's been two years since he won at the All England Club in 2012.
Djokovic • He's lost in the title match at three of the past four Grand Slam tournaments against Murray at Wimbledon and against Nadal at the U.S. Open last year, and against Nadal at the French Open last month. After working for years to break through the Federer-Nadal duo, now Djokovic is part of the elite, trying to hold off the new challengers. "We have these youngsters coming up, fearless on the court, hitting the ball, not caring who is across the net," Djokovic said. "It's good. It gets more attention to new faces and to [a] new wave."
Dimitrov • Greatness has been expected of him for years, and he long ago was given the nickname "Baby Fed," as in Federer, because of a similar all-court style and a smooth, one-handed backhand. Dimitrov is the only man who's won titles on grass, hard and clay courts in 2014. "He moves well; he's a very good athlete; he has variety in his game, which helps him play on all of the surfaces," Murray said after his straight-set quarterfinal loss to Dimitrov. "He's a talented guy."
Raonic • At 6-foot-5 (1.96 meters), he delivers one of the most feared serves in tennis. "It keeps him in the match," Federer said. Raonic lost in the second round in each of his first three trips to Wimbledon but now is the first Canadian man in 106 years to get to the tournament's semifinals.
Matchups • Djokovic is 3-1 against Dimitrov. Both are terrific movers and retrievers, which should make for lengthy exchanges. The points should be shorter in the other semifinal. Federer is 4-0 against Raonic, but the kid did not sound intimidated in the least, saying: "I'm not playing the seven-time Wimbledon champion. I'm not playing a 32-year-old man. I'm not playing a father of two sets of twins which is a very low possibility, I bet, to do. I'm not playing the guy that's won whatever he's won, which I could probably list quite vividly. I'm playing a guy that is standing in my way of what I want to achieve."