Fourteen years ago this month, Roger Federer made history by becoming the first Swiss player to reach world No 1 in the ATP rankings.
This came on the back of him winning the Australian Open for the first time.
Fast forward to this week and another milestone is set to come the 36 year old's way. If he reaches the semi-finals at this week's Rotterdam Open he will go back to No 1 and become the oldest player to sit in the position, beating Andre Agassi, who was 33 when he was No 1 in 2003.
Now before we get ahead of ourselves it is not an automatic slam dunk that Federer will get the top spot. Compatriot Stan Wawrinka, a three-time major winner, is a possible quarter-final opponent.
Wawrinka is recovering from injury but he remains a dangerous opponent when he finds his range and gets his backhand firing.
But, to put this into context Wawrinka has never beaten Federer in a match on a hard court, with his three wins from their past 23 encounters all being on clay, the most recent of which being at the French Open in 2015.
It will be a big surprise if it is Wawrinka who derails Federer this week from going back to No 1 for the first time since November 2012.
Federer is only 155 points behind Nadal, who is on the sidelines recovering from the injury that forced him to retire in the final set of his quarter-final at the Australian Open against Marin Cilic last month.
So, in the unlikely event that Federer does not get the job done in the Netherlands this week it does still feel like a question of when, and not if, he gets the top spot back.
It was the only thing missing from his renaissance in 2017. He had begun last year at No 16 in the world after six months out recovering from a knee injury.
The rest had clearly done him good as he put together a superb year of tennis in which he won the Australian Open and Wimbledon titles, and won five other tournaments as well in a season in which he only lost five out of 57 matches.
The only reason, given he had a 4-0 record over Nadal when the two rivals did meet, was that Federer chose to sit out the entire clay court season. This was done with a view to allowing his body to recover from the rigours of back-to-back Masters titles in Indian Wells and Miami and prepare for Wimbledon.
Nadal was a worthy No 1 over the whole of 2017 as he played a fuller schedule and was competitive on every surface.
But Federer has maintained his impressive form into this year and retaining his Australian Open crown, which was the 20th grand slam of his career, has set him up now for a run as No 1 going into the summer.
When Federer first went to No 1 in February 2004 it was the start of a record-breaking run at the top. His reign lasted 237 weeks until he was knocked off the top spot by Nadal in August 2008.
Now, no-one is expecting a repeat of that this time around as 237 weeks from now is August 2022, when Federer will have just turned 41.
But, he is at the top of his game and it is hard to see a consistent challenger other than Nadal in the short-term.
Novak Djokovic and Andy Murray are both struggling with serious injuries, while the next generation of promising talent such as Alexander Zverev, Grigor Dimitrov, Dominic Thiem and Nick Kyrgios are yet to demonstrate they have the consistency or mental strength to compete regularly for the game's top prizes.
Grand slam titles have clearly been the objective for Federer of late. If he had wanted to be No 1 he could have gone for a more aggressive playing schedule. Even playing just a couple more events would have probably got him ahead of Nadal.
From Graham Caygill
But sitting out the clay season was a choice designed to ensure he was in the best condition possible to try to win Wimbledon for an eighth time, and he would go on to achieve that at SW19 without dropping a set.
Being back at No 1 will be the icing on the cake of Federer's past 13 months success. But it will be only a bonus to him. The real goal is winning more titles and majors and with the make-up of the men's game there is no reason why 2018 cannot be as successful as 2017.
Federer already holds the record for most time spent at world No 1 at 302 weeks, 16 more then next most successful Pete Sampras. That gap is going to stretch this year and it will only add to his formidable legacy he has built up.