- The Greek star is a former Grand Slam finalist
- He was seeded 11th for the tournament.
The first major upset of the Australian Open saw Stefanos Tsitsipas get crushed off the court and out of the tournament in a shock four-set loss to unseeded American star Alex Michelsen.
Tstisipas lost 7-5, 6-3, 2-6, 6-4 at John Cain Arena after establishing himself as a fan favorite when he reached last year's men's singles final.
The world number 12 staged a brief comeback in the third set, but Michelsen, who is ranked 42nd on the ATP tour, fought back in the decisive quarter to record one of the biggest wins of his career.
It is the second consecutive first-round elimination from a Grand Slam for the Greek star, who fell at the first hurdle of last year's US Open when he lost to Australian Thanasi Kokkinakis in four sets.
This victory is the first time Michelsen, 20, has beaten a player ranked in the top 20 at a Grand Slam.
The deciding fourth set was memorable, with the pair trading outrageous winners along with ill-timed errors, the costliest of which was a double fault by 11th seed Tsitsipas on a break point in the ninth game.
The Australian Open dream is over for another year for Stefanos Tsitsipas (pictured), who suffered a shock first-round defeat on Monday.
The Greek fan favorite lost the first two sets to American Alex Michelsen (pictured with Tstitpas after match point), who recorded the biggest win of his career.
It is the second consecutive elimination in the first round of a Grand Slam for Tsitsipas, who also stumbled at the first hurdle at last year's US Open.
A clearly devastated Tsitsipas managed to share a warm hug with the American at the net after match point.
“First of all, I tried to keep my composure,” said Michelsen, who struggled at times with his second serve in the deciding set.
“I knew there was going to be a battle until the end.”
It was the first time since 2018 that Tsitsipas lost in the first round at Melbourne Park.
He lost the 2023 final to Novak Djokovic and also reached the semi-finals at Melbourne Park on three other occasions, but is still searching for that elusive first major title.
Michelsen's opponent in the second round will be Australian wild card James McCabe or Spanish qualifier Martin Landaluce.
Later in Monday's session, world number one Jannik Sinner begins the defense of his title against Chilean Nicolas Jarry.
The two main matches of the evening session involve 24-time Major winner Novak Djokovic and No. 3 seed Carlos Alcaraz.
Coco Gauff is pictured during her straight sets victory over Sofia Kenin on Monday
In a result that went as expected on Monday, Coco Gauff continued her recent run of form, beating fellow American and 2020 Australian Open champion Sofia Kenin 6-3 6-3 to advance to the second round at Melbourne Park.
Reigning French Open champion Gauff was not at her best on Monday.
But she was still too good for world No. 74 Kenin, who is a shadow of the player who won her first Grand Slam title at Melbourne Park in 2020 and then reached the French Open final that same year.
He had also beaten Gauff in two of their previous three meetings, both in majors, but was unable to match him for the No. 3 seed in key moments on Monday.
Gauff, 20, has won her last 10 matches in a row and is on a 19-2 win-loss streak dating back to late September, including titles at the recent United Cup in Sydney, the WTA Tour finals in Arabia Saudi and China. Open.