The versatile 23-year-old, who was heavily linked with a summer switch to Liverpool, was unemployed three years ago after being released by Standard Liege.
Without a club and having little money to his name, Theate considered working in construction after being rejected by a Belgian fourth-tier side.
He used the last of his money saved to hire a personal trainer, with his decision paying off after he secured a contract at KV Oostende following a one-week trial.
After just one season in the Belgian Pro League, the centre-back made the move to join Bologna, where he became a key player under the late Sinisa Mihajlovic.
His time in Italy was short-lived, as Rennes came calling in 2022 as their first-choice target to replace the West ham-bound Nayef Aguerd.
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With just two years of professional football under the belt, Theate joined Rennes on a deal rising to £19million - a record fee for a Belgian defender.
Featuring 35 times in his debut Ligue 1 campaign, he helped the Red and Blacks finish fourth in the table to secure a Europa League spot.
A permanent starter in their Europa League campaign so far, Theate has helped Julien Stephan's seal their place in the knockout stages.
His impressive performances in the early stage of his career saw him earn a spot in Roberto Martinez's 2022 World Cup squad for Qatar.
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And while he failed to feature in the Middle East, he has since been capped on 13 occasions - starting all eight Euro 2024 qualifiers at left-back.
Speaking to Ligue 1, Theate revealed how a conversation with idol Sergio Ramos continues to inspire him in his quest to become an elite defender.
He said: "I love the mentality of Carles Puyol and Sergio Ramos.
"They inspire me a lot with their grit and hunger to win every game. Incidentally, I bumped into Sergio Ramos on holiday this summer.
"We chatted for a while about everything, including the French league and our respective careers.
"He told me that I'd made a good choice in coming to Rennes and that the most important thing was to get as much playing time as possible to progress."
Describing his rapid rise to prominence, the youngster remarked: "It was a bit rock and roll during my early years, as I played for Genk, Standard Liege, Genk and Standard again.
"When I was 20, I was kicked out and found myself without a club, unemployed.
"That was at the end of the 2019/20 season, just after the start of the COVID crisis. I started looking for a 'real' job because I had to earn money to live.
Theate continued: "I was going to work in construction because I don't have a degree - I sacrificed my studies.
"I was preparing for a life other than football, but I never gave up. During COVID, I used the little money I had saved to pay for a physical trainer and to be ready if an opportunity arose.
"In fact, before Oostende, I tried out for a Belgian D2 club and was turned down. I was told I wasn't up to scratch."
Theate could be set for a big move in the future, with it remaining to be seen if former admirers Liverpool rekindle their interest.
French news outlet L'Equipe suggested in the summer that the player was considered by Jurgen Klopp who was keen on bringing in a left-sided centre-half.
A move failed to materialise, but with Joel Matip currently out injured - and in the final year of his contract at Anfield - Theate could find himself back on the Reds' radar in January.
And with the Merseyside giants in a battle for the Premier League title, defensive reinforcements in the New Year could be seen as a priority.
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Whether he joins Liverpool or not, it's clear to see that Theate is destined to join a European powerhouse.
And should he have half the career his idol Ramos has had, he could very well go down as one of Belgium's greatest defenders of all time.