The Worcester prop could line up for Wales next Saturday when New Zealand kick off a possible Grand Slam tour of Great Britain and Ireland.
And it will represent a remarkable achievement by the 27-year-old, who has twice fought back from cancer and now put himself on the threshold of an international career.
Horsman only qualified for Wales last month, having completed a three-year residency period, but he is so highly rated by Wales coach Mike Ruddock that a Test call-up beckons, either against the All Blacks or when Fiji arrive in Cardiff next week.
"You don't play rugby to not have these chances, and if I am lucky enough to be involved on Saturday, then that is what you want," said the former Bath forward.
"You want these situations, that is why you train for all those hours and make all the sacrifices. Wales v New Zealand, it just doesn't get any bigger than that.
"To play rugby for Wales is like playing football for Brazil. It's just the highest honour, and once you have played over in Wales and been involved in Welsh rugby, you can't help but want to aim for that goal," he added.
"I have worked hard for the last three years to get myself into this position, and I am just very excited.
"I am not the sort of person who gives up easily, and I have been quite single minded about getting this opportunity."
World champions England are fully aware of Horsman's powerful scrummaging ability, but he has no regrets about taking the alternative route to potential international stardom.
"It wasn't so much that I gave up any ambitions to play for England, but I came over to Wales and started to enjoy my rugby again," he added.
"As flattered as I was when Andy Robinson phoned me, it wasn't a matter of giving up anything.
"I had already made my decision but I didn't want to turn around and say to everyone. I am not playing for England because I have chosen to play for Wales.
"Basically, I just wanted to get on with my game and hopefully get a chance of being in the Welsh squad.
"I just didn't want to make a song and dance about it - I prefer to do my talking on the field, to be honest."