Walker says he's enjoyed the "journey".
He said: “I've come a long way from the area where I grew up in Sheffield to that loan spell at Northampton, which was my first taste of real professional football, to sitting here looking forward to the World Cup.
“It's been a journey. But I've enjoyed it and just want it to continue.
“Going to Northampton back then was a massive opportunity for me. I'd been in the academy at Sheffield United, who were in the Championship, and Northampton were in League One when I went there.
“Stuart Gray was the United manager and he gave me the chance to go and show what I could do really. From then, it's history. But I can still remember driving down with my mum and dad. They were in the front car and I had to follow them down because I'd never driven on a motorway!
“They even came in and watched me train after we arrived. Adebayo Akinfenwa was there and Leon Constantine.
“And I was thinking, 'These guys are going to think I'm just a kid who's turned up with his mum and dad!'
“It was like a first day at school – I think I only played 13 games there. But they were so valuable. Some of those players depended on winning games for their mortgage. So it was a massive learning curve to go down there and train with the senior players."