Sportal.co.nz 19.Oct.2013Getty Images
Richie McCaw and wing Cory Jane have been ruled out of Saturday's Bledisloe Cup match with a tight calf and a minor hamstring tear respectively.
Despite the absence of McCaw, who boasts 120 caps to his name, New Zealand were well equipped in the loose forwards with Sam Cane, Horwill said.
"Obviously anyone that's played 120 Tests is a pretty big hole to fill, but Sam Cane's an excellent player," said Horwill.
"He's been playing very well and I don't think they'll lose too much. It's hard to replicate that experience but I think Sam Cane has done a good job when Richie hasn't been there."
Horwill added New Zealand's leadership stocks wouldn't be too affected given incumbent leader Kieran Read's history of leading the team in McCaw's absence and didn't expect it to be much of a shock.
Australia are looking for their first win over New Zealand since they claimed the 2011 Rugby Championship. They're also searching for an historic win in New Zealand that would break a 12-year drought.
Despite finishing third in the Rugby Championship there were causes for optimism amongst Ewen McKenzie's men when they ran in seven tries to hammer Argentina 54-17 in Rosario almost a fortnight ago.
"The belief in the individual player is certainly better for coming off a win than not," he added .
Horwill said his side had a lack of self-confidence at the start of the international season courtesy of a 'whirlwind' few months that included a change in coach, the respective systems and the introduction of 12 uncapped players to the team since the start of the international season.
"I think there was maybe a lack of confidence in the way we wanted to play and uncertainty in what we were trying to do.
"Guys were a little unsure about what was happening and I think certainly spending time together, playing games together – you can't replicate that by throwing guys together.
"We've worked very hard with that. I think we're at a better place now than where we were as a group."
New Zealand aren't the only side to be affected by injuries. After starting his Wallabies career in the No.10 jersey, Matt Toomua moves a spot to second five-eighths to cover for injured goalkicker Christian Leali'ifano. Playmaker Quade Cooper will be in charge of the goalkicking duties.
The match kicks off at 7.35pm at Dunedin's Forsyth Barr in what is the first Bledisloe Cup match held in the city for 12 years.