Croft, the Leicester and England flanker, broke his neck in three places and burst a disc in April 2012 when he mistimed a routine tackle on the Harlequins number eight Nick Easter.
The 27-year-old was operated on the following day by leading spinal surgeon Peter Hamlyn, who had to go in through the back of Croft's neck to compress the nerves and through the front to reconstruct the vertebrae.
In a complex procedure, Croft had the "crazy paving" removed, a bone graft taken from his hip and a metal plate, cage and screws inserted into his neck.
Hamlyn later told Croft he had beaten the odds - he had come as close as was possible to being paralysed by an injury which could have killed him.
Many players may have counted their good fortune at having avoided a catastrophic injury and called it a day. Instead, Croft set his mind on a comeback when he jets off to Australia.
"When I got injured I was just hoping to get back and playing and I was very fortunate to be involved at the end of the Six Nations," Croft said.
"My train of thought was getting on to the England tour of Argentina. That would have been a massive bonus and a highlight for me so being included in the Lions squad has far surpassed that."
Croft's comeback was inspired by his close friend Matt Hampson, the former Leicester prop who was paralysed when a scrum collapsed in an England Under-21 training session in 2005.
"Hambo helped. He is one of the most upbeat characters there is, especially what has happened to him," Croft said.
"It would very easy for him to become a recluse but he is out there doing things for the foundation and it gave me that little bit of hope that if anything did happen it was not the be all and end all.
"You play a contact sport so there is potential for things to happen, a very small percentage. But Hambo has come through it and achieved massive things. It gives you that hope."
Croft starred for the 2009 Lions in South Africa, scoring two tries in the first Test as the Lions mounted a comeback against South Africa and then produced a performance of even greater stature a week later in Pretoria.
It was a career-defining tour and Australia offers him the chance to take his game to even greater heights.
Croft put on five kilograms during his time out injured and he has returned stronger but, as Harlequins discovered in the Aviva Premiership semi-final, he has lost none of his electric pace.
"Playing for the Lions has been the highlight of my career so far," Croft said.
"I was very happy with the way that tour went but it's not just about trying to recreate that, for me it's about moving on from that.
"I think it is impossible to recreate that Lions form exactly anyway. So I have to bring the best of that into my game, as well as everything else I am doing."