St Kilda mature-age recruit Tim Highmore will make his AFL debut in Sunday's clash against the Giants.

The Saints confirmed in a statement on Friday morning that the defender will play his first game in the GIANTS Stadium clash.

Highmore, 22, was drafted to the club with Pick 45 in the 2020 National Draft and now gets his opportunity amid a host of injuries in the backline, with Jarryn Geary, Ben Paton and James Frawley all sidelined.

"It will be great for him to play and he's really looking forward to it," Saints coach Brett Ratten said on saints.com.au.

"He kicks the ball well, he's brave, he's a good size… so whether he's a second-tall defender or third he's sort of in that category.

"There's so many stories about how you got an opportunity to play the game... some have had to work (through) different paths and different challenges.

"Players have got their own stories, but they all have the opportunity to make a mark on their own AFL careers."

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Ratten in an earlier interview in February described Highmore as a "(Callum) Wilkie clone".

“Young Tommy Highmore is nearly a Wilkie clone in the way he goes about it, but he’s a right-footer and he played exceptionally well mopping up,” Ratten said.

“He kicks the ball well, he’s brave, he’s a good size… so whether he’s a second-tall defender, or third, he’s sort of in that category.

“Is he going to play round one? We’re not sure. Is he going to play this year? We’re not sure.

“I had a one-on-one meeting with him the other day and we spoke about that; it’s about getting your opportunity and taking it and he’s up for the challenge.

“At 22, he’s a long-term view too, for us. Whatever he does this year will be a bonus because he will improve, he will adapt to the AFL (and) the way it’s played.

“He’s already mentioned: ‘Gee, it’s a bit quicker, if you don’t get your positioning right you get caught out’. And I’m like: ‘Exactly’.”

St Kilda and GWS will meet at GIANTS Stadium on Sunday at 3.20pm AEDT.