The 27-year-old English-born, Welsh-bred tight-head prop, who will represent the Northern Hemisphere against their southern counterparts in London, could nail his colours to the mast of either country - but it will almost certainly be Wales when he completes his residential qualifications in May.
Wales will reap the reward for getting in first with Horsman revealing that, despite his huge performances in Worcester's powerful pack which looks set to ensure the newly-promoted Warriors retain Zurich Premiership status, England have shown hardly any interest.
But he has caught the eye of Lions coach Sir Clive Woodward who chose him for tomorrow's IRB Aid match for the Tsunami survivors with this summer's New Zealand tour in mind.
Modest Horsman is playing it all down.
"It's great to have been called up but the most important thing is the cause itself," Horsman said.
" Just to be part of helping so many people is a great thing because everyone knows someone who was out there or had been out there before.
"My sister was out travelling the year before and she's hoping to go back this summer to do some volunteer work so if I can help as well that's fantastic.
"I'm not looking at it in a Lions context. Obviously this is a great chance and I want to do well but there are all the other props playing in the Six Nations.
"I'm the only uncapped player and my first aim at the moment is to try and get international rugby," he said.