Whilst Stefanos Tsitsipas cemented Greece’s progress last night at the United Cup it was new tennis prodigy, Stefanos Sakellaridis, who caused one of the biggest upsets at the tournament following his undisputed dominance over a player ranked more than six times higher.

The 18-year-old up-and-coming star, currently seeded No.830 in the world achieved a 5-7, 6-1, 6-3 win over Belgium’s Zizou Bergs who is world No.129.

Interestingly, Sakellaridis entered the match as a last minute substitute following his teammate’s Michail Pervolarakis’ withdrawal due to an injury.

“I was getting prepared because I knew that my teammate has an injury and I might play,” Sakellaridis said after beating Bergs while everyone on Team Greece cheered him on.

Notably, the teen is competing without a racquet sponsor and was close to running out of strings this week, according to tennis commentator Robbie Koenig.

Sakellaridis played with a fully maintained racquet for the first time in months.

The Greek teen, paid tribute to a member of the tournament stringing team during his on-court interview, thanking the staff for solving an ongoing issue.

“I was competing for the last two or three months, [but] I was using only one racquet,” explained Sakellaridis later.

“I had grip problems with all my racquets, so I didn’t want to use any others. I was only using the same racquet because it was the only one that felt like the grip was how I like it. That racquet, after I played with it a bit, the butt cap [at the bottom of the handle] started moving, so in the past month I was playing with one racquet, and the grip was moving. Then I came here, and he fixed all my racquets, so now I can freely play.

Great story today in Perth at @UnitedCupTennis as 803rd ranked, 18yr old, Steafanos Sakellaridis, achieves the biggest win of his career over Bergs…SS with only 3 racquets here (No sponsored racquets), all 3 butt caps were loose, coming off…

— Rob Koenig (@RobKoenigTennis) January 3, 2023

“Of course… You can see that the team chemistry is unbelievable,” Sakellaridis said when asked how he felt being cheered by such enthusiasm by Stefanos Tsitsipas and Maria Sakkari as well as his sister Sapfo Sakellaridi.

“You can see that the team chemistry is unbelievable, so… It’s a huge boost for every one of us to play much better. When you feel good, you play good.”

“It was the first time in my life this week seeing a Top 100 player in front of me, actually. When everyone was coming by, like Goffin, Dimitrov, I was like, ‘Oh, wow’.”

Especially when it comes to Stefanos Tsitsipas, Sakellaridis said that seeing such huge outburst of emotion towards him from his “role model” meant the world and gave him even more confidence against his much experienced opponent.

Sakellaridis of Team Greece on RAC Arena in Perth on Tuesday. Photo: Tennis Australia/ Mark Peterson/Supplied

“To be able to live with [Tsitsipas] throughout the day, you can see how much work he puts in and my respect towards the top players has grown immensely,” said Sakellaridis.

“Stefanos has given me lots of advice, he has helped me a lot. Also all the team, they seem like they really want to help me, all of them gave me advice. Obviously from watching here, what they do and how they do it on the court and outside the court, I can also see some things for myself. All in all it is an amazing experience to come here.”

Following Tuesday’s remarkable win Sakellaridis went away not only with 20 Pepperstone ATP Ranking points but also $25,900 in prize money, what he described as a career-changing moment for a starting-out Greek athlete.

“It’s my ATP debut, and it came with a win, and prize money that I couldn’t imagine,” said Sakellaridis.

“[After the United Cup] I’m going to compete in Monastir for the next few weeks. There is a 15K ITF tournament there, but we’ll see how it goes. It was a big win and a big step up in the rankings.”

Team Greece is brimming with confidence for the inaugural United Cup. Photo: Tennis Australia/ Trevor Collens/Supplied