Since then, their careers have taken vastly different paths.
Swiatek has won four more grand slams and reached No.1 in the world, while Raducanu struggled at times with injury and the crushing pressure that comes with being the next big thing in British tennis.
Swiatek, 23, crushed Slovakian Rebecca Sramkova 6-0 6-2 in the second round at Melbourne Park on Thursday, while the unseeded Raducanu was made to work considerably harder before ousting close friend Amanda Anisimova 6-3 7-5.
The Pole has won all three of her previous matches against Raducanu and sits 59 spots above her on the world rankings.
Iga Swiatek (pic) will be the heavy favourite in her third-round match against Emma Raducanu. (Lukas Coch/AAP PHOTOS)
"Honestly there's no point to look at rankings, especially when you have these great players (like Raducanu) who have already been through great tournaments and won some tournaments," said Swiatek, who pocketed her first major aged 19 at the 2020 French Open.
"You know that they can play well.
"Maybe they're not consistent to have the ranking, but still, you need to be on your toes and ready because you don't know what they'll show this week."
Raducanu showed plenty against Anisimova, hanging tough after requiring medical treatment for back spasms in the second set.
Britain's Emma Raducanu also progressed to the last 32 without dropping a set on Thursday. (Lukas Coch/AAP PHOTOS)
Before arriving in Melbourne for the Open, Raducanu had not played since mid-November.
"It's incredibly difficult whenever you play a friend, it adds another dimension to the match and not necessarily a pleasant one," said Raducanu, who was just 18 when she created tennis history at the 2021 US Open when she became the first player - male or female - to win a major in the Open era as a qualifier.
The 23-year-old Anisimova had advanced to the fourth round on three of her previous five visits to Melbourne Park.
Raducanu felt the gulf in the rankings meant there wouldn't be all that much in the way of external expectations on her against Swiatek.
"You always have the pressure that you put on yourself to perform to your best ability, which is not really going to change, but that's every match," she said.
"But I think I'm going to enjoy playing in a great atmosphere.
"I'm looking forward to going out there and testing my game against the best, because ultimately that's why you play tennis, and you live for these matches.
"It's going to be a great buzz of adrenaline."
No.8 seed Emma Navarro from the US was pushed to three sets for the second straight match before edging China's Wang Xiyu 6-3 3-6 6-4.
Emma Navarro was pushed to the limit in her win over Wang Xiyu. (Joel Carrett/AAP PHOTOS)
Navarro went down a break early in the final set and then reeled off the last four games in succession to advance to a round-of-32 showdown with Ons Jabeur from Tunisia.
Jabeur, a former world No.2, advanced with a 7-5 6-3 win over Colombian Camila Osorio.
Former Wimbledon champ and No.6 seed Elena Rybakina from Kazakhstan ended the campaign of highly promising American wildcard Iva Jovic with a 6-0 6-3 win.
Playing her 10th Open, Russian No.9 seed Daria Kasatkina equalled her best performance at Melbourne Park by cruising into the third round with a thumping 6-2 6-0 win over China's Wang Yafan.
Tenth seed Danielle Collins overcame a raucous Kia Arena crowd and a scare from Australian Destanee Aiava to claim a 7-6 (7-4) 4-6 6-2 victory on Thursday night and tee up a third-round clash with fellow American Madison Keys.
For her part, Keys fought out a dramatic three-set win over Elena-Gabriela Ruse, beating the qualifier 7-6 (7-1) 2-6 7-5.
