Eight of the world's best players take centre stage at the ATP Finals from Sunday (November 15), an event where Roger Federer still holds a record that may never be broken.

Across his illustrious career, Federer was victorious at the year-end tournament on six occasions - second only to Novak Djokovic - while holding the record for most final appearances (10).

The 20-time Grand Slam champion remarkably won the tournament in three different locations, lifting the trophy in Houston, Shanghai and London. But it was during his 2005 triumph in Shanghai when Federer achieved brilliance that may never be replicated.

Roger Federer hit a double bagel at the 2005 ATP Finals

Federer was almost unstoppable at the peak of his powers, possessing arguably one of the most lethal forehands in history, combined with a smooth and repeatable serve.

The legendary Swiss star had almost everything in his armoury that enabled him to become a great in the sport, showcasing these attributes during his dominance in the mid-2000s.

Across five ATP Finals appearances between 2003 and 2007, Federer won four of them, but in the only year during that period when he didn't win (2005), he still made history.

In his semi-final against Gaston Gaudio in Shanghai, he secured a rapid 6-0, 6-0 victory, becoming the first and still the only player in the tournament's history to hit a double bagel.

Gaudio admitted in his press conference afterward that he couldn't wait to get off the court. “I’m sad about it. I’m so disappointed. But what can you do? It happens in life," Gaudio said. "There are things a little bit worse than this sometimes in life."

Although the 2004 Roland Garros champion took the defeat well, he did make an eyebrow-raising prediction about Federer five years earlier, labelling him "terrible" while saying he would never reach the top of the rankings.

"He’ll never be number 1 in the world," said Gaudio about a then-teenage Federer. "He can’t hit a backhand, how is he going to be number 1 in the world? I don’t think he’s any good.”

In becoming one of the greatest to pick up a racket after spending a whopping 310 weeks as number one, the Swiss superstar of course proved Gaudio horribly wrong, later seeing the funny side of his outrageous prediction.

“How wrong I was! The best ever, in history!” he exclaimed after watching his sharp rise to stardom.

Roger Federer once suggested change for ATP Finals

Alexander Zverev, Carlos Alcaraz, Ben Shelton, Daniil Medvedev, Flavio Cobolli, Arthur Fils, Frances Tiafoe and Rafael Jodar will all compete at the men's showpiece event.

The tournament is structured in a round-robin format, with eight singles players/doubles teams divided into two groups of four. The winner of each group is placed in separate semi-final brackets, with the top player/team in Group A playing the runner-up in Group B, and vice versa.

Up until 2007, the championship match at the ATP Finals was contested in a Grand Slam-style best-of-five format, but since then, every final at the event has been just best-of-three.

After beating Jo-Wilfried Tsonga in 2011, Federer was asked if the tournament should go back to the best-of-five format, preferring the excitement that came from the longer matches.

"I think so. I think so. I mean, if it’s a match like this, it’s fine," Federer said at the time. "I think it’s still enough tennis for the people. I think it’s exciting. We had the whole scenario today in today’s match. But if I had served it out, it would have been over in a hurry.

“I think I almost felt the spectators weren’t quite ready for it to end quite yet, although many would have been happy for me; they would have loved to see more tennis. I remember sitting in a room in Shanghai where players were asked, Would you like it to be five sets or three sets, the year‑end final? Kind of went in a circle. Everyone said best‑of‑three sets.

“I was the only guy that said, I think we should have best‑of‑five sets. Okay, let’s make it best‑of‑three sets. I don’t care. I do care, actually."