While he did acknowledge the issue, he felt the 3-2 home loss to Arsenal was multifaceted.
"If I thought fixing defensive set-pieces was the answer to us bridging the gap then I'd put all of my time and effort into that," Postecoglou said afterwards.
"But that's not where we're at.
"For us it's about, when I was focused on the details of, not just set-pieces but a lot of moments in games where we don't sense that you give good opposition the time and the space to do things then they're going to hurt you.
"I think they maybe had four attempts on goal in the first half and they conceded three. I don't think it's about one part of it, I think it's a bigger, broader picture than that, but our defensive set-pieces for those two were very poor. But there's a lot more than that to fix.
"There are thousands (of details)," Postecoglou continued.
"It's the little details like you can't give time and space to the opposition, you can't make decisions or lose focus in any given moment.
"The transition goal we were focused on a decision at the other end when we should have been thinking about the danger that was potentially at the other side."