Postecoglou has been impressed by Spence in preseason.
“With Djed, I had an open mind. I certainly think the kind of characteristics he has would fit into our football," Postecoglou said ahead of their clash at Leicester on Monday night.
“It’s then more about, 'OK, well he obviously didn’t fit last year, will he fit this year?'
“He’s had a good pre-season. He’s trained really well. He seems to have fit into the group really well.
“I don’t think left-back is his obvious position, I think he’s more of a right full-back, but the fact that he can play out on the left again gives us some good options into the season where with European football we’re going to have more challenges.
“It was quite obvious last year that whenever we had disruptions in terms of injuries or suspensions, our performance dropped a fair bit. We’re trying to narrow that gap. Hopefully having Djed as part of our squad allows us to do that.
“He’s training well, he’s available for Monday and I’ll make those decisions at the weekend."