Roger Federer will reclaim the number one ranking for the first time in more than five years after overcoming Robin Haase to reach the Rotterdam Open semi-final.
Not since November 2012 had Federer topped the rankings but the evergreen 36-year-old became the oldest man to reach the summit thanks to Friday's 4-6 6-1 6-1 victory.
Federer, who accepted a wildcard to the tournament earlier this month, will replace Rafael Nadal when the rankings are updated on Monday.
Afterwards, the 20-time grand slam champion told reporters: "It's a little bit surreal. The first time I got back to number one was in 2004, a long, long time ago. It was more than five years since I was last number one. It was particularly nice today as I had to go and get it, win a match. Back in 2012, I won Wimbledon and a week later, when I was on holiday, I found out that I was number one."
Federer, who won his sixth Australian Open last month, did not have it all his own way against Haase after dropping the opening set.
But the Swiss maestro recovered, racing out to a 3-1 lead in the second set before winning nine of the next 10 games to seal his place in the final four.
"I thought I was pretty calm," Federer added. "I woke up, I had a good sleep and then watched the Winter Olympics for three-four hours, before I headed on-site. I had a normal warm-up and had a good routine. I knew what I wanted to do and how I wanted to play. I was backing myself and I was confident. A lot of people have asked me today how I handle all of the pressure. But I think it helps all of the big matches I've played over the years.
"Losing the first set, definitely got my head spinning a little bit. It reminded me that I had to go and get the victory (Friday). It wasn't going to be handed to me. I had to change my plan and started to play more aggressively.
"I will enjoy the moment. I've already had a glass of [Moet & Chandon] champagne and I'll have another one later on. I'll play late again tomorrow [Saturday], so I can have a good sleep and enjoy myself. It's incredibly special and I'm so happy. Severin [Luthi] also flew in tonight, so it was an extra surprise too."
Next up for Federer is lucky loser Andreas Seppi, who defeated Daniil Medvedev 7-6 (7-4) 4-6 6-3.
On the other side of the draw, Tomas Berdych's withdrawal prior to his quarter-final handed fourth seed David Goffin a walkover.
The Belgian meets second seed Grigor Dimitrov in a rematch of last year's ATP Finals showpiece after the Bulgarian defeated Andrey Rublev 6-3 6-4.
|Muller apologises to Tagliafico for kick to the head|
|Pereira pleads for more Manchester United chances|
|Griffin hails ´phenomenal´ Lowry after Warriors demolition|
|I´ve played with Zidane and Henry, but Messi is something else – Pires|
|Dragons forward Jack de Belin charged with sexual assault|
|Durant: Raptors are the real deal|
|Cocu bids farewell to Fenerbahce after ´mutual agreement´ is made over October sacking|
|Australia unchanged for historic Perth Test|
|Champions League draw: The possible last-16 ties|
|Southee happy to be back on home soil|
|I wouldn´t swap Dembele for Neymar – Pires|
|Canelo ready to risk heavy weather against Fielding|
|Raptors upstage Warriors, Davis leads Pelicans with 44 points|
|India skipper Kohli excited by green Perth wicket|
|PSG? I haven´t decided my future yet – De Jong|
|Marcelo: Real Madrid don´t have attitude problem|
|India pair Ashwin, Rohit ruled out of second Test|
|Kovac: Ajax-Bayern draw was amazing|
|Sims re-signs with Dragons until 2022|
|Derrius Guice injury update: Redskins RB (knee) has rehab setback, undergoes 3 more procedures|
|Emery: Arsenal could sign defender in January|
|Phillies sign McCutchen to three-year deal|
|O´Neal thinks his Lakers teams could ´easily´ beat Warriors|
|A-League to add two clubs by 2020|
|Curry says he was ´obviously joking´ about moon landing comments|
|Now the beautiful part starts – Ronaldo ready for Champions League knockout stage|
|Bayern have a lot more potential – Lewandowski not satisfied despite top spot|
|Lyon star Fekir shares plaudits for Champions League progression|
|Mourinho not surprised by United´s defeat to Valencia|
|Motivation no issue for Benfica, claims Vitoria|
|Lewandowski finishes Champions League group stage as top scorer|
|Mourinho: We scored two goals and lost 2-1!|
|England have a diamond - Guardiola hails City´s Foden|
|Sterling´s carefree display invites us to love football more than others hate|
|Juventus achieved their objective, despite everything going wrong – Allegri|
|Never say never - Schmidt not ruling out All Blacks role|
|Bologna´s winning start ended in BCL|
|Di Francesco critical of Roma performance|
|Shakhtar Donetsk 1 Lyon 1: Fekir fires French side through in Group F|
|Benfica 1 AEK Athens 0: Grimaldo sends hosts out on a high|
|Young Boys 2 Juventus 1: Hoarau double seals famous victory|
|Manchester City 2 Hoffenheim 1: City through as group winners after Sane brace|
|Ajax 3 Bayern Munich 3: Kovac´s men clinch top spot in Amsterdam thriller|
|Valencia 2 Manchester United 1: Jones scores own goal as Red Devils limp through|
|Solari accepts responsibility for Madrid´s heaviest home defeat in Europe|
|WATCH: Rooney backs Rocky ahead of Canelo showdown|
|McLaren to collaborate with Team Bahrain Merida|
|Las Vegas to host 2020 NFL Draft|
|Stade teenager tragically dies after neck injury|
|Cahill may need to leave Chelsea if he wants to play, admits Sarri|
|Viktoria Plzen 2 Roma 1: Chory winner takes hosts into Europa League|
|Real Madrid 0 CSKA Moscow 3: Champions humiliated at Bernabeu|
|Sarri condemns ´disgusting´ Sterling abuse|
|Hansen hails outstanding Ben Smith ahead of Pau switch|
|Foden, Sterling start for Manchester City v Hoffenheim|
|Sky decision will not affect us in 2019, insist Froome and Thomas|
|Al Ain 3 Team Wellington 3 (aet, 4-3 on penalties): Shootout heartbreak for semi-pros in Club World|
|Jackson to remain Ravens´ starting QB despite Flacco return|
|Rams headline 2019 NFL International Series home teams|
|Rams headline International Series home teams for 2019|
|Atlanta want ´exciting football´ from new boss amid Bielsa links|
|Atlanta still yet to receive ´serious´ bid for ´Bale-like´ Almiron|
|Tottenham v Manchester United to be held at Wembley|
|Matip facing six weeks out with fractured collarbone|
|I´ve had quite a lot of calls – Brailsford encouraged by Team Sky interest|
|Afghanistan Football Federation president provisionally banned by FIFA|
|Knee injury rules Huddersfield´s Mooy out of Asian Cup|
|Arnautovic tipped for Man United move by Austria team-mate Sabitzer|
|Arsenal legend Adams to become RFL president|
|My love for football still burns strong – Toure speaks out amid talk of Premier League return|