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.
|Wizards to face Knicks in London next season|
|Vettel eyeing Paul Ricard profits - French GP in numbers|
|Malaga turn to Muniz once again|
|Amrabat: VAR doesn´t work if you do not use it|
|Suarez earns 100th Uruguay cap|
|You´ve got to look beyond football - Denmark chip in to fly new father Knudsen home|
|Neymar returns to Brazil training after injury scare|
|No passports required - Burnley´s 51-year wait for European tie sees Clarets draw... Aberdeen|
|Huddersfield bring in Bacuna to boost midfield|
|Forget the GOAT and the goatee - just enjoy Ronaldo and Messi|
|Ronaldo bearing down on Daei after going past Puskas - The top five goalscorers in international foo|
|Portugal 1 Morocco 0: Record-breaker Ronaldo sends Renard´s men out|
|Halep pulls out of Eastbourne International|
|Brazil v Costa Rica: Coutinho ready for more Selecao toil|
|Muller and Bierhoff dismiss reports of German disharmony|
|Mooy can play at a higher level, says Socceroos boss Van Marwijk|
|Remarkable Ronaldo breaks Puskas´ European record|
|Belgian Grand Prix deal agreed until 2021|
|Isco: I´m not going to speak to Ronaldo again!|
|Slater expects to be fit for Origin II|
|Curran and Overton added to England ODI squad|
|Hussey fears Australia will be left with ´mental scars´|
|Fabianski swaps Swansea for West Ham|
|Loftus-Cheek ready to replace Alli|
|England are a team now - Rashford|
|Lazaridis calls for Cahill to start against Denmark|
|Arzani and Ryan can play at the highest level, says Bosnich|
|Dust (Ja)pan and brush: Blue Samurai fans clean up in Saransk|
|Lodge reaches agreement over New York attack|
|Gerrard can become a strong manager - Arena|
|Arsenal target Torreira has left for €30m, says Sampdoria chief|
|Murray unsure over Wimbledon participation|
|De Gea has to bounce back from Ronaldo shocker - Bosnich|
|Martinez not looking for perfection|
|Farah´s Wests Tigers return confirmed|
|Cubs get extra-inning win to split doubleheader with Dodgers|
|Denmark will ´struggle´ if Australia stop Eriksen, says Jakobsen|
|Astros´ win streak ends at 12|
|Lahm backs Germany, Low after losing start|
|Messi has all our support – Dybala|
|Strickland apologises for ´stupid decision´ that led to broken hand|
|Five-time Open Championship winner Thomson dies aged 88|
|´Positive´ Pogba not bitter towards media, says Varane|
|Portugal privileged to have ´humble´ Ronaldo, says Pepe|
|Strickland breaks hand punching door after blown save, out for up to eight weeks|
|He will have received good money – Costa delighted by Griezmann extension|
|Kane: Pochettino sent me love hearts after World Cup heroics|
|Nationals place Adams on 10-day DL with broken finger|
|Dybala: I can play alongside Messi|
|Lewandowski: Poland didn´t take enough risks|
|England´s Kane aiming to reach Ronaldo, Messi levels with World Cup performances|
|Kicker given three-year match-fixing ban|
|England confirm Alli thigh injury|
|Federer through, Zverev out in Halle|
|Back on the map and earning letters from ladies, Tabarez embraces Uruguay´s heritage|
|Rampant England rout Australia in record-breaking display|
|Pulisic in right place at Dortmund, says Arena|
|Wilshere confirms Arsenal exit|
|NASCAR at Sonoma: TV schedule, standings, qualifying drivers for Toyota/Save Mart 350|
|Muguruza and Kvitova cruise through in Birmingham|
|Leno among top 10 most expensive goalkeepers|
|Pained Salah unable to halt Russia´s unlikely march|
|Kyrgios downs ´legend´ Murray as Dimitrov and Djokovic progress|
|Neymar pain normal – Coutinho unconcerned by ankle issue|
|Russia 3 Egypt 1: Salah strikes but hosts right on course for last 16|
|We must make Ronaldo less exceptional, says Morocco boss Renard|
|Chandimal handed one-Test ball tampering ban, faces further ICC charge|
|Arsenal sign goalkeeper Leno from Leverkusen|
|Mexico style in Germany win surprised Arena|
|Monaco complete €20m move for Lyon teenager Geubbels|