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.
|Director of rugby Kennedy leaves London Irish|
|Brilliant Bale basks in Wales record|
|Romo hits back-to-back birdies on PGA Tour debut|
|Neuer needs to play to make Germany´s World Cup squad – Low|
|All we can do is take it on the chin - Bayliss responds to Auckland humiliation|
|China 0 Wales 6: Record-breaking Bale leads demolition job in perfect start for Giggs|
|Curry closer to return than Durant - Kerr|
|Alonso expects McLaren to be at ´lowest level´ in Melbourne|
|Serena´s conqueror and a new tennis superstar - who is Naomi Osaka?|
|Bale becomes Wales´ record goalscorer with China hat-trick|
|Hamilton warns Ricciardo not to rock Red Bull boat|
|It could have been worse! England´s lowest Test totals|
|The ´reality for people with a brain´ is Manchester United are in transition, Mourinho claims|
|Black Caps seamer savours Boult from the blue|
|West Ham ban disruptive fans for life after Burnley chaos|
|Storm respond by beating Cowboys|
|Ten wickets in 79 minutes - a timeline of England´s Auckland horror show|
|England´s bleak winter sinks to new low|
|Iniesta hints at post-World Cup international retirement|
|All we do is talk s*** - Pique goads Madrid stars over WhatsApp|
|England like rabbits in the headlights - Bayliss|
|Euro 2016 humiliation helped England, claims Dele Alli|
|58 all out! Shambolic England overshadow Broad milestone|
|Iniesta confident of two more years in Barcelona starting XI|
|Kane probably the best striker in the world - Maguire|
|Broad strikes again – the Opta data behind the England bowler´s 400th wicket|
|Wenger told Wilshere he could leave Arsenal|
|An India hat-trick and THAT Ashes annihilation: Broad´s finest Test spells|
|Broad removes Latham to claim 400th Test wicket|
|If you play for Atletico, you must be committed – Koke responds to Griezmann speculation|
|LeBron´s historic night leads Cavs past Raptors, Howard tallies rare 30-30|
|Del Potro, Cilic loom for Haase and Herbert|
|Giggs: Bale will feature for Wales in China Cup|
|Serena releases statement after skipping media following Miami loss|
|England bowled out for 58 in 130-year Test low|
|Maradona: Messi doesn´t have to prove himself by winning World Cup|
|Cavs tally worst defensive half of season against Raptors|
|McIlroy, Johnson stunned on day one in Austin|
|Cristiano Ronaldo hasn´t asked to leave Real Madrid amid China links – Perez|
|Oakland Athletics allowing fans to pick price of tickets, all proceeds to charity|
|Ginobili: Spurs not expecting Kawhi Leonard to return this season|
|Trout, Angels brass confident Shohei Ohtani will be a star|
|Osaka wanted to impress Serena with stunning Miami Open win|
|Manchester United apply for professional women´s team|
|Bolt hopes fellow Jamaican breaks his world record|
|Bolt a fan of Ronaldo, but compares his talent to Messi´s|
|Outstanding Osaka knocks out Williams in Miami opener|
|Del Potro ´tired´ heading into Miami Open|
|Heynckes definitely leaving at end of season, claims Ze Roberto|
|Joshua tells Wilder to be ´realistic´ in negotiations|
|Shaw issue a distraction from Manchester United´s failures, says Neville|
|Hamsik withdraws from Slovakia squad|
|RFU backs Jones despite awful Six Nations|
|Hamilton eyes Melbourne pole record, 100 club for Vettel? - Australian GP in numbers|
|Griezmann backs Pogba to prove doubters wrong for France|
|Sanchez ´expected something better´ from Manchester United move|
|WATCH: Thomas conjures up great escape in Austin|
|Javi Martinez in the dark over Spain squad omission|
|Jones should have managed England workload - Flood|
|Giggs feeling the tension ahead of Wales debut|
|Juventus confirm Alex Sandro thigh injury|
|Hart praises ´loyal guy´ Southgate amid World Cup axe fears|
|Windies singing in the rain as they clinch World Cup spot|
|I miss Morata, says recalled Costa|
|I can improve even more at Manchester City - Bernardo Silva|
|Neymar will be fit for the World Cup, insists Ronaldo|
|Costa thinks Griezmann will stay at Atletico Madrid|
|Third DRS zone added for Australian Grand Prix|
|Ferdinand worried by England´s World Cup striker options|
|Hamilton an F1 great - Fittipaldi|