The team will begin play in 2023, but Carnell is keen to get started and bond with a city that has as rich a soccer history as any in the country, and match the energy of those employees who are already on board.
"When I started engaging with front office and ownership and talking with them, and just hearing the energy that they portray on a daily basis, the humble nature of these individuals in the front office, my first impression blew me out of the park," he said in an exclusive interview with ESPN. "I can't imagine how hungry the city is."
Carnell, 44, joins St. Louis after spending the past five seasons as an assistant with the Red Bulls, a period that included a spell as interim manager in 2020 following the dismissal of Chris Armas. During that time, New York went 6-5-3, helping the Red Bulls qualify for the postseason.
"The way I felt I went about it just gave me ambition and an appetite for more," he said of his time managing the Red Bulls.
Carnell also lost his father, George, six months ago, and coping with that loss provided him with the impetus to step out of his assistant coach's role on a more permanent basis.
"I didn't want to be in a position to be like thinking in five years' time, 10 years' time, and then all of a sudden, the opportunity, it's too late, and you will be this assistant coach forever," he said. "That why I decided to punch into this and take this opportunity."
For St. Louis sporting director Lutz Pfannenstiel, Carnell's modest amount of first team managerial experience wasn't a hindrance. Instead, the South African checked two important boxes, one being a familiarity with MLS and the other a preference for a high-pressing style.
But Pfannenstiel also has a shared a bit of history with Carnell. Back in 2015, Pfannenstiel taught a three-week coaching course on behalf of the German Football Federation, the DFB, and one of his students was Carnell, who finished top of the class.
"It just starts molding your mindset and framing your mind where you want to take this thing and plants a few seeds of growth," said Carnell. "Eventually, now we're seven years down the line, and I'm sitting here at the table today. So my ambition grew, my hunger grew. And just applying that with the energy on a daily basis. And I've just done it by being me."
Pfannenstiel was so impressed that made a mental note to keep an eye on Carnell as the years passed. His protégé's successful interim stint in New York confirmed Pfannenstiel's belief that Carnell was ready.
"He showed what he can do. He turned the fortunes around," he said of Carnell's time in charge of New York. "He had a very, very good body language. I saw his growth. I saw the way he speaks to the players. I saw how he can implement things and that interim period with the Red Bulls, I think that was just that final straw which gave us that little extra [confidence] that he's our perfect choice."
Pfannenstiel added that he feels Carnell's style will be a perfect fit for the organization and the city.
"I think people here like to have a hard working team, a modest team, a team which gets out there and leaves every single piece of energy on that field," he said. "We want to create an atmosphere that we'll not just have a hungry head coach. You want to have a hungry team."
As a player, Carnell spent the bulk of his career in Germany, suiting up for the likes of VfB Stuttgart, Borussia Monchengladbach, Karlsruher SC and Hansa Rostock. In his native South Africa, Carnell played for Wits University, Kaizer Chiefs and Supersport United.
At international level, Carnell made 42 appearances for South Africa and was part of the team that played in the 2002 World Cup.