Roger Federer insists he is only slightly surprised to find himself tantalisingly within touching distance of a record eighth Wimbledon title despite his 36th birthday fast approaching.

The Swiss star reached the Wimbledon semi-finals for the 12th time on Wednesday with a 6-4, 6-2, 7-6 (7/4) win over Milos Raonic.

It was his 100th match at the All England Club and the 50th Grand Slam quarter-final of his career.

At 35, Federer is the second oldest man to reach the semi-finals after Ken Rosewall who finished runner-up in 1974 at the age of 39.

With 'Big Four' rivals Andy Murray and Novak Djokovic suffering injury-hit exits on Wednesday and Rafael Nadal having lost in the fourth round, Federer is favourite to reclaim the Wimbledon title on Sunday and break the tie for seven he has shared with Pete Sampras since 2012.

It would also take him to 19 career majors and make him the oldest champion at Wimbledon in the Open era.

"The plan was always to hopefully be strong later on in my career," said Federer who will face Tomas Berdych in Friday's semi-finals.

"I don't see myself playing better than a few years ago. I always hope to improve every year.

"I'm just very happy that I'm still doing so well. Am I surprised? Maybe a little bit." 

The contrast between Federer and Murray and Djokovic on Wednesday was impossible to ignore.

Defending champion and World No.1 Murray lost in five sets to Sam Querrey of the United States, hobbled by a long-standing right hip injury.

Djokovic, the three-time winner, quit after two games of the second set of his quarter-final against Berdych with a right elbow injury.

Like Murray's hip, the elbow problem plaguing Djokovic has been a constant menace for many seasons.

It has got so bad that Djokovic admitted he is contemplating either surgery or even an extended break from the sport.

Federer has already trimmed back his schedule, skipping the 2016 and 2017 French Opens which were won by Djokovic and Nadal.

After losing to Raonic in the 2016 Wimbledon semi-final, Federer shut down his season to rest a knee injury which had already required surgery earlier in 2016.

He came back in January 2017, won the Australian Open for his 18th Slam, added the Indian Wells-Miami Masters double before hibernating again through the claycourt season.

"Once you hit 30, you've got to look back and think of how much tennis have I played, how much rest did I give my body over the years, how much training have I done, did I do enough, did I overdo it or not enough," he explained.

"It's always calibrating the whole thing. For me it worked out. Sometimes the body and the mind do need a rest."