Coach Michael Cheika started both in the the back row in four matches at the last World Cup four years ago and in other games.
While Australia reached the final in 2015, questions remain over the impact playing both simultaneously has on the lineout and Australia’s back row balance.
“I’d actually prefer David Pocock to come off the bench, I think in a World Cup team you need a big back row,” Horan said on Tuesday.
“Michael Hooper captain, yup, (No.8) Isi Naisarani has been going well, who’s the six?
“Has Lukhan Salakaia-Loto done enough at six to earn that spot again? It probably depends on who you’re playing. You might have a David Pocock on the bench and bring him on at halftime.
”I just don’t think we can go too deep in the competition having Hooper and Pocock in the same back row starting.”
While Cheika on Tuesday was still exploring the possibility of England-based lock Will Skelton being included in the World Cup squad to be named on Friday, Horan advocated removing restrictions on overseas-based players.
Skelton isn’t contracted to Rugby Australia, and doesn’t meet the 60-cap Giteau Rule threshold for players attached to overseas teams,
“I get the Giteau rule, I get the 60 Test matches, but I’m a big believer in a World Cup year you should be able to select anyone from around the world,” Horan said.
“Where they are playing it doesn’t matter. Get the best team that gives us the best opportunity to win a World Cup.”
He insisted uncapped highly rated young back Jordan Petaia should make the squad.
“I wouldn’t say it’s a risk selecting Jordan Petaia, I think he’s going to be a sensational player and he could be one of the great players,” Horan said.
“Hopefully if we get dry pitches in Tokyo and around Japan we’re a really good chance of going deep,” he said.
“Because we’re not wet trackers, we don’t play well in wet weather conditions.”
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