Compounding the Wallabies’ woes was the fact that hooker Josh Nasser was also forced off early in the second half.
“It’s very hard to keep up with things when they happen that quickly,” Schmidt said.
“Allan and Angus Bell came off at halftime, but then you know you’re skinny, you can’t afford to lose another prop.
“And then Slips got an HIA right at the start of the second half.
“And Josh Nasser, about the 55-minute mark, he kept cramping.
“We were hoping he could actually keep playing, but in the end, that just wasn’t going to be possible.
“I’ve been involved [in] coaching over 100 test matches, and I’ve never seen that before [with that many front-row injuries in such a short space of time].”
Schmidt, who coached Ireland from 2013-2019, said having to rotate the captaincy so many times during the match was hard to deal with.
“No disrespect to Harry, but it’s a little bit destabilising when you work your way through and you get to your fourth captain,” Schmidt said.
“Harry wouldn’t have had the expectation that he was going to be leading the side when we started the match.”
The Rugby Championship loss in Perth followed the Wallabies’ 33-7 defeat to South Africa in Brisbane.
But Schmidt praised his team’s fighting effort at a wet Optus Stadium, believing they showed grit and determination in the face of adversity.
The Wallabies now face two tough tests against Argentina in Argentina, starting on September 1.
Prop Taniela Tupou, who recently flew to Tonga for his father’s funeral, will return in time for the trip to Argentina.
Nick Frost (concussion) and Jeremy Williams (concussion) will also be available for selection, but inside centre Hunter Paisami is in some doubt with a leg injury.
Schmidt said Will Skelton wasn’t realistically in the selection frame given the powerful lock is tied up in pre-season training with his Top 14 side La Rochelle.
“I continue to have conversations with Will,” Schmidt said.
“But it is complicated to get someone like Will back out of the Top 14 lead-in... they’re in pre-season training.”