More than a year on and the 32-year-old is living that dream as the head of sports science and analysis at Championship club Bristol City.
With the ambitious Robins out to earn promotion to the Premier League, Costin is enjoying the ride.
Originally from the South Australian town of Gawler, Costin threw out a comfortable job in education at St. Martins Lutheran College to relocate to England.
“Growing up I always played Aussie Rules. I used to love English football as well but I never really played it because I was so focused on playing Aussie Rules,” Costin told The World Game.
“And then, as I got into my 20s, I started playing a bit more football. I’d always supported it, staying up late watching the SBS games. I think it was just the opportunity [that appealed].
“I always wanted to work in sport and I see football as a world game – it’s played in so many countries – so I really wanted to work in that. The A-League, for what it is, is really good but there’s only 11 teams (now 12), so there’s only 11 internships going.
“So I knew that the chances of being able to get an internship and fund it whilst living in a city like Sydney or Melbourne was not going to be available. My mother was born in the UK and moved to Australia when she was 10 so I’ve got a British passport.
“So I thought, 'if I really want this, I’m going to have to uproot and head across and see what can happen and just hope for the best' – and that’s what I did.
“I quit my job as head of sport and PE teaching, which I’ve been doing for eight years, and moved to the other side of the world knowing that if I wanted it enough then that was what was going to have to happen.”
Costin studied a Bachelor’s degree in Education and in Health Services at Flinders University, before later going on to study educational leadership and then earn a Master’s in High Performance Sport from the Australian Catholic University.
Two years ago, he approached nearly half of the professional clubs in the English pyramid, before eventually earning a role with League Two side Stevenage.
“I got turned down by 35-40 clubs for an internship,” Costin explained.
“I couldn’t get anyone to give me an internship for the 2018-19 season. Then into the 2019-20 season I couldn’t get anyone to give me a go either. Eventually Stevenage gave me a go and I managed to get an internship there.
“And then, after four weeks, I got made head of sports science. I’m a believer in life-long learning, coming from an education background, so I was always trying to better myself and better my learning. So that took me to Brentford just for a visit.
“And then my real break came, I went to Sparta Prague for a couple of days while I was working at Stevenage. I spent time with Ben Ashworth over there who was a physio at Arsenal for many years and now he’s the director of performance at Sparta Prague.
“It was basically that connection, so after Christmas I got a call from Andrew Rolls who’s the head of performance at Bristol City.
"He said, 'I’ve love to have a chat with you', and it kind of went from there. We met up for a coffee and he said, 'show me what you do', so I showed him everything and he was impressed.
“We just clicked and I started over at Bristol in March and here I am I guess.”
Costin joined Ashton Gate in March and is in charge of monitoring the players’ output in training and games, analysing data and workloads to help manager Dean Holden.
“A lot of what I do is around athlete monitoring and loading, so subjective questionnaires in the morning, or post-match screenings, in terms of fatigue monitoring,” he explained.
“Then on the pitch, doing all the GPS stuff and clipping all of that, basically making sure we’re hitting targets that we should be during the week to optimise our performance come game-day. It’s a very big club. I’m loving it over here at the moment.
“We’ve got a really good staff to work with, a really good club culture as well and that’s pleasing. We’re very well-resourced, both in terms of facilities. It really is a massive club.
“In terms of all the technology, having all that stuff is so helpful because a lot of the clubs in the EFL don’t have those resources.”
The Robins have made a strong start to the season and sit in the playoff places after 15 matches.
The south-west English club have never made it to the Premier League but are out to win a spot in the top flight.
“That’s the goal of the organisation,” Costin said.
“I think they’ve been around the mark for the past couple of seasons but just kind of faltered late. This year we started really well, we haven’t really had blips - yes we’ve had losses and draws but no consistent blips along the way.
“So it’s just a matter of pushing on and keeping everyone available for Deano the manager, making sure we can keep everyone on the park and do the best we can come the back end of the season when the games are going to come thick and fast. The Championship is a gruelling league.”
Costin’s journey has been one of determination and persistence, but the South Australian refused to die wondering and wanted to have no regrets.
"People at the time said it was a huge gamble but I don’t think it was,” he admitted.
“I always believed in myself and backed myself a fair amount of the time. Education was always going to be there to go back to I think, so whilst it was a risk, I’d called it a calculated gamble.
“Everybody said I was crazy, quitting a job that was good and chasing a dream, that’s not what people do.
"But I think you have to do it, otherwise you’re going to die wondering. I’m just so grateful for the opportunities presented to me.”