"I'll be up against a lot I suppose," Castle said.
"I know I can't really miss any balls against him, otherwise it is frame over."
That was a lesson that
China's Ding Junhui
delivered to Castle in devastating fashion at the International Championship in Chengdu earlier this month, claiming a 6-0 win in the round of 128 on the way to the title.
"It was a big experience," Castle said.
For prodigious potter Castle, however, taking on Selby at the Barbican Centre it is just another step in his meteoric rise.
He first picked up a cue at the age of seven, was competing regularly a year later and dominating junior snooker from age nine. Castle has since gone to win multiple junior English championships and narrowly missed out on becoming the youngest ever European Under-21 champion in 2012.
Mark Selby wins 2012 UK Championship title in late-night thriller
With his parents having supported his early desire to turn professional soon by allowing him to leave school, Castle is in a hurry to make his name in the sport.
When he starts talking about wanting to turn professional at 16, the parallels with five-time world champion O'Sullivan, who did the same in 1992, are clear.
The Southampton youngster does not want the comparison to simply stop there either.
"I want to be world champion - that's the dream," Castle said.
"I've got a lot time ahead of me and I want to get on the [professional] tour by 16 and play in all tournaments instead of just getting picked for one."
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