Roger Federer's 2019 loss to Grigor Dimitrov ranked as greatest men's upset in US Open history

Grand Slam tournaments have thrown up plenty of shocking results over the years. There have been several big upsets in the 21st century alone, even when the likes of Serena Williams, Roger Federer, Rafael Nadal and Novak Djokovic have dominated the circuit.

Recently, as part of its Relay series, Tennis Magazine looked through the annals of the US Open - which according to them "has a history of head-turning results" - to identify the most shocking upsets of all time. And their findings were rather unexpected to say the least.

On the women's side, CiCi Bellis' win over Dominika Cibulkova at the 2014 US Open was ranked the biggest upset in US Open history. But the men's pick was more recent, and also perhaps more unpopular - Grigor Dimitrov's win over Roger Federer at US Open 2019.

Grigor Dimitrov's first ever win over Roger Federer finds a place in history

Roger Federer (L) and Grigor Dimitrov at the 2019 US Open

Tennis Magazine ranked the upsets according to points based on a dedicated system explained here. And the 2019 quarterfinal matchup between Grigor Dimitrov and Roger Federer accumulated more points than any other men's match.

The Swiss maestro had not reached the semifinal in four years at the time, but was the overwhelming favorite against a player who was seemingly out of form coming into the tournament. Federer also had a commanding 7-0 lead over Dimitrov before that match. In fact, the man people once called 'Baby Federer' had only ever taken two sets off his idol prior to their Flushing Meadows meeting.

But despite winning the first set and then later building a two-sets-to-one lead, Roger Federer couldn't get the job done. He ended up losing 6-3 4-6 6-3 6-4 6-2, thus allowing the Bulgarian to reach his maiden US Open semifinal.

The result got 179,029 points, even though the Swiss seemed to have picked up an injury towards the end of the fourth set. It may come as a surprise to some that Roger Federer's shock defeat in the previous year, to John Millman in the fourth round, didn't earn the top spot.

Novak Djokovic (L) and Kei Nishikori at the 2014 US Open

Rafael Nadal's defeats to Lucas Pouille in 2016 and to Fabio Fognini both featured on the list too, as did Kei Nishikori's win over World No. 1 Novak Djokovic in the 2014 semifinal. The Japanese international had gone on to lose to Marin Cilic in the final that year, after the Croat had famously defeated Roger Federer in another shock result.

On the women's side, while CiCi Bellis' win in 2014 over was ranked first, the next four were all Serena Williams defeats - against Roberta Vinci (2015), Bianca Andreescu (2019), Victoria Azarenka (2020) and Naomi Osaka (2018).