Roger Federer has failed to add to his 88 titles this year. (Source: AP)

Fifteen years after famously stunning Pete Sampras at Wimbledon, seven-time champion Roger Federer returns to the All England Club with his career at a crossroads and his confidence at crisis point.

The 34-year-old Swiss, holder of a record 17 Grand Slam titles, is without a major since Wimbledon in 2012 and is enduring arguably the toughest year of his career.

Injury forced him to skip the French Open ending a streak of 65 successive appearances at the Slams stretching back to 1999.

He has failed to add to his 88 titles this year, his longest drought since 2000 and has suffered back-to-back semi-final losses in Stuttgart and Halle, both on grass which has been his preferred surface of domination.

In an indication of changing times, his last-four loss in Stuttgart to Alexander Zverev was his first against a teenager in 10 years.

But the Swiss star is adamant that he can still be a winner even if clinching an eighth crown at Wimbledon would make him the oldest ever champion in south-west London, surpassing Arthur Ashe who was a month shy of his 32nd birthday when he lifted the trophy in 1975.

“I think if my movement gets better and then the baseline game improves a little bit, I’ll be better on the big points, on the return and also in less trouble on my own service games,” said Federer.

“But I’m okay and I’m pleased. I’m feeling now we’ve got enough time before Wimbledon to get ready for that.”

The fact that Federer has reached the last two Wimbledon finals is testament to his capacity to surprise both his supporters and doubters.

The problem, however, is that he lost both those championship matches to Novak Djokovic, the world number one who currently holds all four majors and is halfway to the first calendar Grand Slam since 1969.

Djokovic leads their head-to-head only by 23-22, but has claimed their last four clashes at the majors. Federer hasn’t defeated the Serb at a Slam since the Wimbledon semi-finals in 2012.

“Is Djokovic now the man to beat? Absolutely. Does he deserve to be where he is? 100 per cent. But is he beatable? Yes, of course he is. I beat him three times last year,” Federer told the Guardian this week.

Wimbledon has always been Federer’s home-from-home even if his first two visits as a pony-tailed contender with a short fuse and dream one-handed backhand ended in first round losses.

But his fourth round defeat of seven-time winner Sampras in 2001 marked him out as the American’s natural heir even if 2002 saw a woeful first round exit to Mario Ancic.

That blip was forgotten 12 months later when he won his first Wimbledon, spiking the heavy artillery of Mark Philippoussis in the final.

Since then, he has enjoyed more successes than setbacks. Federer won the title every year between 2003 and 2007, adding two more in 2009 and 2012.

In between, he lost the 2008 final to Rafael Nadal in what is widely-regarded as the finest men’s championship match in history, a five-set epic which ended in semi-darkness.

However, there was also a shock second round exit to world number 116 Sergiy Stakhovsky in 2013.

Federer was 31 then and the career obituaries were being composed. They have been dusted off a few times since.

“Don’t you understand that playing tennis is great fun? I don’t need to win three slams a year to be content,” he told the Guardian.

“If the body doesn’t want to do it, if the mind doesn’t want to do it, if my wife doesn’t want me to do it, if my kids don’t like it, I’ll stop tomorrow. Zero problem.”