However, it was his inability to train for Sweden's Under-21 international squad due to blood poisoning that saw him uncover his hidden talent - music.
"The doctor said I wasn't allowed to train or do anything," Walker told FIFA.com.
"What am I going to do? I can't play PlayStation all day long. I bought a guitar and I started to write a few songs. I suppose you could put it down to not being able to train and do what you've been doing all your life, I was just looking for something to fill that.
"It was a fluke that I ended up in Idol. They called me up after seeing little clips from an open mic thing. It's grown to something I didn't dare to dream of."
Walker, now 25, went on to win Sweden's version of American Idol, and continues to juggle both of his talents after recently signing for Djurgardens in the Allsvenskan - the top tier of Swedish football.
He has sung with the likes of British pop star Robbie Williams, and has represented Sweden - one of two nations he is eligible to play for, along with the Republic of Ireland - at Under-17 and Under-19 levels.
"It's been a hell of a ride for me and the experience of a lifetime to be involved in the Swedish pop [show] Idol," Walker said.
"I'm really privileged to have been a part of it and to have gotten a new career, combining the two. I have to be smart and use my time wisely.
"It's probably been the best footballing year in my career. I'm looking forward to these next three years with Djurgardens."
Walker said he has made it clear in his contract with Djurgarden that his music will not clash with his football, despite matches with his former club GIF Sundsvall being forced to be moved due to his Idol commitments.
"We have it in the contract that everything I get approached with, musically, I run by the club and ask them if they think it's alright and we take it from there," Walker said.
"I don't miss a single training session, match or team meeting. I'm totally committed to the football.
"What I do on my spare time, that's a different story. If we train, and we're free after lunch - I go home and pick up the guitar and write songs, that's my business."
Walker released an album, titled 'Belong' in 2013 - that went to number two in Sweden.
At just 25 years of age, there is plenty of time to see if he belongs on the football field.
