The Wallabies will be stronger with a fully-fit Kane Douglas in the squad than they would be with James Horwill "at his best", believes 1991 World Cup-winning coach Bob Dwyer.

Dwyer agrees Horwill's game lifted under Wallabies coach Michael Cheika after a Super Rugby season in which the Queensland Reds lock was part of a rudderless and underperforming side.

Cheika even credited Horwill, who captained Australia in the 2011 World Cup, for playing himself "into contention" for his 31-player World Cup squad when he announced it last Friday.

Horwill played strongly for the Wallabies off the bench against the Springboks in Brisbane. With fellow Reds lock Rob Simmons out injured after their win against Argentina in Mendoza, which Horwill was not picked for, he started in the two Tests against the All Blacks – in Sydney (won) and Auckland (lost).

But for his four World Cup second-rowers, Cheika overlooked Horwill for Douglas, whose only game time since a back operation in March was 17 minutes off the bench against the All Blacks in Auckland.

Cheika, who coached Douglas at the Waratahs before he joined Irish club Leinster that he left in late July to return to Australia, clearly believes Douglas in peak condition offers more than Horwill.

Cheika also believes Douglas has time to rediscover that peak with the Wallabies to play the US Eagles in Chicago on September 5 before their World Cup opener against Fiji on September 23.

As does Dwyer, who said: "Had I been discussing it a couple of months ago, I would say, 'Horwill is no chance.' Then I saw him play much better under 'Cheik' than he has played for years.

"But I've no doubt that we are more of a chance to win the World Cup with Kane Douglas playing at his best than we are with James Horwill playing at his best.

"[Douglas] was our No.1 lock when he went away. If 'Cheik' thinks there is no worry and he has had him in camp for a couple of weeks, he knows what he is basing his judgement on."

Dwyer warns against underestimating Cheika's train of thought, citing as an example his selection of only two rather than three hookers in his squad – captain Stephen Moore and Tatafu Polota-Nau.

Under World Cup rules, if either are injured they must be withdrawn from the squad for another hooker to be brought in. If not, a player already in the squad with hooking skills must cover for that position.

Cheika has not named who would provide that cover, but Dwyer believes Cheika will have had one of his five props up-skilled for the role by his Argentinian set-piece coach, former Pumas hooker Mario Ledesma.

"Two hookers is risky, but I'm 100 per cent confident he has something in mind for that," Dwyer said.

From Cheika's options among the props, Scott Sio might be the most likely candidate to cover as a third hooker with experience in the position at schoolboy level.