Everywhere he looked, the 16-year-old saw someone he recognised from the television screen - after all, his father John says "we've got the Big Bash on pretty much every night at home".

But this was more than a chance to do the bat flip - the Twenty20 tournament's answer to a coin toss - in the Sydney Thunder's clash with the Melbourne Renegades on Wednesday.

It was a chance, if only for a few moments, to push aside the 18 months of cancer treatment which began after pain in his knee led to an osteosarcoma diagnosis.

"He went to a physio for all of that, and in the end he was referred to get an MRI. They found a tumor in his knee," Williams' mother Brownen said.

"In October he had his knee replaced and they put a growing prosthesis in, so that can actually extend.

"He was meant to finish treatment in April and he relapsed straight away. We're still trying to find something that'll work for him. He's now on some tablets, hopefully that will work.

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"He had some radiation last Friday up in Sydney. All of our treatment is being done up in Sydney. It's horrible, having to travel up there all the time.

"He's been a champion through it all. We're all getting a bit tired now, as you'd expect, it's been 18 months. It's a tough slog for a kid.

"Mitch has been very excited all day. He was pumped, he doesn't show a lot of emotion but he was pretty excited.

"We were talking about practicing, but he didn't get off his Playstation all day so there was no practice."

One can imagine the surprise the family received on Wednesday morning when a Thunder official called and said "we want Mitch to do the bat flip".

"Flipping the bat was a good feeling. You pretty much half control the game ... not really," Williams said with a smile.

"It was good meeting the two captains, Dan Christian and Callum Ferguson. Dan Christian is one of my favourite players, so it was cool meeting them.

"It's very special to do things like this, especially through such a tough time."