Former Test captain Horwill led Australia at the 2011 World Cup and spent the final years of his career in the northern hemisphere with Harlequins in England.
He has kept a keen eye on rugby in that part of the world and is adamant there is one thing the Wallabies need when the showpiece returns to Australia next year.
"We've seen the way the game's going, the way the Six Nations was played ... the physical battle's really important," he told reporters at an event marking 500 days until World Cup kick-off.
Hulking lock Will Skelton changed last year's British and Irish Lions series with his barnstorming form after missing game one through injury.
An Achilles tear will keep the French-based talent sidelined for the rest of this year, leaving a gaping hole to fill for coach Joe Schmidt and then Les Kiss, who will take over in August.
Horwill thinks there is a clear frontrunner in Salakaia-Loto.
Salakaia-Loto who was unable to crack the Wallabies squad until the Lions had left town, despite sensational form in a series of tour games in his own injury return last year.
The Queensland Reds lock has continued to torment defences this season and, after missing Saturday's loss to the Western Force to be with his pregnant wife, will be back on the frontline to face Moana Pasifika this weekend.
"A guy like Lukhan's been outstanding. I expect to see him play a part with Will Skelton injuring himself," Horwill said.
"That enforcer type player ... he's been exceptional for the Reds and they missed him against the Force.
"He's had some injuries so hopefully stays fit and I can see him ... being a critical member for us because that's the way the game is going."
Horwill also thinks incumbent Test captain Harry Wilson has rediscovered his best form in the last two weeks following a long 2025 season while battling a knee injury.
"On the weekend he was trying to single-handedly drag that Reds team over the line," Reds premiership captain Horwill said.
New Zealand teams currently occupy the top four spots of the Super Rugby Pacific ladder with two rounds to play.
But Horwill has seen enough "green shoots" to offer confidence the Wallabies won't suffer a repeat of their disastrous 2023 World Cup campaign, when they were eliminated at the round-robin stage for the first time.
"We're getting that confidence from beating New Zealand sides ... we're getting over that mental hurdle that some may have," he said.
"I'm very confident that we'll go deep into the World Cup next year.
"You can't rely on just 15 players. Joe's been working on building that depth and getting those combinations right.
"In key positions, there's competition for spots."
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