As far as Lions comebacks are concerned, the twinkle-toed former Ospreys and Wales wing, who is the third highest try scorer in world rugby history with 60 in 91 games for Wales and The Lions, is about to upstage them all when he flies in from Japan to take on the Australian Conference Super Rugby winners in Canberra.
"It was completely out of the blue," Williams, who was initially due to fly to Australia to commentate on The Lions, rather than play for them, told talkSPORT.
"I never thought I would ever get this opportunity again, but if me contributing on Tuesday is going to help the Lions squad be successful in the three Tests then that is what I am here to do.
"Rob Howley (Lions assistant coach) phoned me. It's still sinking in. I'm over the moon, and what I will do on the field is give 100% effort and commitment and do whatever it takes to help the team out."
Williams was a double try scorer in his last appearance for The Lions as Britain and Ireland's elite stunned the Springboks 28-9 in Johannesburg four years ago.
He scored a last-gasp try for Wales against the Qantas Wallabies in his final match for his country in December 2011 but carried on playing rugby, first with the Ospreys and then with the Mitsubishi Dynaboars in Japan.
And while he may have experienced a step down in the overall standard of the competitions he has been performing in since heading to Asia, Williams says he has no concerns whatsoever about producing a display worthy of the shirt he will wear on Tuesday.
"If I had any doubt whatsoever that I wasn't capable or good enough then I would have said no, because there is no way I will let the Lions down," added Williams.
"I have been playing in Japan over the last 12 months. Fitness is not going to be an issue. I get into Sydney on Monday morning, and I am training at about half past 10."
Shane Williams' Lions record
|11/06/2005||New Zealand Maoris||19-13|