The Worcester prop arrived home from a two week family break in Greece with his expectant wife Angie, son Dan and daughter Grace at 1am and was woken by a phone call at 8am asking him to jump on a plane before he'd even managed to unpack his bags.
Horsman has the sympathies of Wales team manager Alan Phillips, who had a similar experience when he was called up to the bench in Australia 24hrs before a Rugby World Cup match with Ireland in 1987, but he arrived in Brisbane safe and well this morning (Friday) and was immediately involved in a line-out session.
"I must admit I felt a little disorientated after napping this afternoon," said Horsman. "I woke up and found myself wondering around the hotel corridor looking for the kids before I realised I'm on the other side of the world and they're probably fast asleep at home with their mother.
"But there was no hesitation for me when I got the call. It was a real easy one. I'd watched the first Test in a bar in Greece and it was really exhilarating, it made me want to come out there and then and play in the second game.
"So I've probably been willing it to happen all week. Not that you want anyone to get injured, but all I knew was I wanted to play and I have the full support of my family who were great about it.
"We gave Australia a real game last week and we are determined to do the same thing tomorrow (Saturday). Ceri (Jones) will do a great job in Adam's absence, he's an extremely capable player who I've come up against myself in the English league when he's turned out for Harlequins. I'll be telling him to go out there and enjoy it and I'll be right behind him if needed, but he'll go well, he's got what it takes and we are all backing him."
Phillips's services were not required for the 1987 World Cup game in the end, but he says he was well prepared to do his bit for his country, just as Horsman is now.
"As it happened I didn't get on the field in that game in '87, but I was there ready, willing and able to do so," he added.
"That's the kind of thing you do when your country calls and if Chris is needed on Saturday he'll turn up and give everything he's got to the cause. It's a measure of the man he is that he didn't even hesitate. He's itching to start, never mind sit on the bench, we'll make sure we look after him tonight and he'll be ready, there's no doubting that."