At 36-years-old, it is absolutely remarkable how much Federer continues to achieve.

After dominating the sport throughout the 00's, the Swiss legend suffered a collapse in form earlier this decade and did not win a Grand Slam title for just under five years.

Suffering from numerous injuries and with Novak Djokovic, Rafael Nadal and Andy Murray to compete with, many believed that his career in the sport was rapidly reaching an end.

But Federer eventually broke that hoodoo by claiming the Australian Open last year, and he has gone from strength to strength ever since.

Buoyed by a change in schedule which has kept him fresh going into tournaments, Federer followed up his Australian Open triumph by winning his eighth Wimbledon title last year.

And he made it three Grand Slam victories in just 12 months on Sunday night, having overcome the challenge of a spirited Marin Cilic to claim his sixth Australian Open title.

FEDERER CONFESSES HE FELT HE WOULD LOSE

Given that Federer had accomplished everything there is to achieve in the sport, many would have suspected the Swiss to be his ordinary laid back self during this year's tournament in Australia.

However, that was not the case - made apparent by his emotional reaction to winning his twentieth Grand Slam where he broke down in tears whilst being given the trophy.

And Federer has since revealed the self doubt he felt throughout the tournament, and even claimed he was convinced he was going to taste defeat at some point.

Speaking about Sunday's final against Cilic, Federer revealed how he was overcome by nerves after winning the first set.

"I had a good start to the match [then] I think I lost the second because of nerves, to be honest," he said.

And when asked why he felt so many nerves during this tournament, Federer stated: "You can't explain it sometimes.

"It is just a feeling you get. It's like against Berdych, I felt, like, 'I'm probably going to lose this one.' I was not negative, but I just felt like I saw a loss was coming somehow.

"This year seems more surreal. I can't believe I was able to defend my title after all these years, that I could do it again."

FEDERER HAS NO IDEA HOW LONG HE WILL CONTINUE

Federer is dominating the sport well into his thirties, but he has admitted he does not know how long he will able to maintain this success for.

When asked how long he can keep up this level for, he said: "No idea. Honest, I don’t know. I have no idea.

"I’ve won three slams now in 12 months. I can’t believe it myself. I just got to keep a good schedule, stay hungry, then maybe good things can happen.

"I don’t think age is an issue, it’s just a number. But I need to be very careful in my planning, really decide beforehand what are my goals, what are my priorities.

"I think that’s what’s going to dictate how successful I will be."