The former University of Pretoria and AmaZulu head coach joined Stellies in 2017, spending nearly nine years at the club.
He transformed the Cape Winelands team from a First Division side into a solid Premiership competitor and even secured third place on the standings in the 2023/24 season.
Barker also led the team to their first top-flight silverware when they won the 2023 Carling Knockout Cup, alongside two MTN8 final appearances.
"Not many people are aware, but I was in the final year of my contract, and I'd spoken to the club about an extension and moving forward," Barker told FARPost.
"Unfortunately, it took a while, and by the time December arrived, I hadn't yet secured a contract for the following season.
"Then Simba called, and I saw it as an opportunity to go to a club that challenges for league titles and cups."
Barker added: "It was a big team on the continent, so I felt that, at this stage in my career, it was an important move for me to go and coach and try to win league titles."
During his short time with Simba, Barker has already won two trophies, including the CRDB Bank Federation Cup and the Muungano Cup. His team also finished in second place on the Tanzanian Premier League standings last term.
