5 records that will likely elude Roger Federer forever

#3 Best win% in a season

Federer poses with 2005 ATP Finals (then called the Tennis Masters Cup) winner David Nalbandian

Federer produced one of his most dominant seasons in 2005. Following losses in the semifinals of the Australian Open (Marat Safin) and French Open (Rafael Nadal), Federer lost only one other match all year before arriving to the final of the 2005 ATP Finals, then called the Tennis Masters Cup.

Having won 81 matches in the season, Federer was a win away from equaling John McEnroe's mark of 82-3 (96.5%), which is the best success rate in a single ATP season.

On a 35-match win streak (the sixth best in the Open Era), Federer was also on a record 24-match win streak in tournament finals. Having beaten David Nalbandian in the group-stage of the tournament, Federer was an overwhelming favorite for the title - which would have helped him record the joint-best match win% in an ATP season.

Nalbandian led 4-0 in the fifth before Federer fought back, and he was a service game away from winning the title at 5-4. But the Swiss maestro faltered at the last hurdle and fell in the ensuing tiebreak, ending the season with a 95.3% win rate.

Federer would not come close to equaling or surpassing McEnroe's mark again. A 92-5 win-loss record in 2006 and a 54-5 record in 2017 have been his only other 90% win-rate seasons since then.

With the Swiss losing more frequently these days, often to lower-ranked players that he would have swatted aside in his prime, he is not likely to come anywhere close to McEnroe's record of the best win% in a season again.