For the second week in succession the centre-back's error gift wrapped the opposition their opening goal with Inverness eventually triumphing 2-1 at Greenhill Road.
It was also the second time this term Inverness prevailed over the Paisley men by a 2-1 margin and despite Buddies boss Danny Lennon opting to shuffle his defensive formation with a back three, Saints were once again largely the architects of their own demise.
This second successive defeat was also the first occasion Saints have lost back-to-back games this season and means they drop out of the top six.
With a trip to rock- bottom Aberdeen next, Buddies boss Lennon will have to galvanise his men.
But Carey is keen to be positive and jumped to the defence of his team-mate McAusland: "Marc is one of the best footballers at St Mirren and you see that every day in training.
"The manager encourages us to pass the ball out from the back and that puts a lot of responsibility and extra onus on the centre-backs in particular.
"Marc got unlucky with his pass being cut out, but he stuck to it and showed a lot of character to put that behind him and finish the game strongly.
"You win and lose as a team and we did not do enough to get something out of the game."
The Buddies now head to Pittodrie desperate to put an end to their losing run and Carey says they will bounce back.
He said: "The Aberdeen game is now a very important one for us. It is vital we don't continue to develop a negative momentum and with them bottom they will be fighting tooth and nail on Saturday to get a result."
Despite an encouraging start for Saints, McAusland gifted the lead to their opponents when his ill-judged cross field pass to Jim Goodwin was intercepted by Jonny Hayes and he fed Andy Shinnie who side-footed home past the exposed Craig Samson.
But they got back on level terms right after the interval when Steven Thompson rose majestically to head home from a Gary Teale corner.
The former Rangers striker and Teale both went close to putting Buddies ahead, but it was Inverness who took the lead when Jonny Hayes bent a superb 20-yard effort round Samson to restore Inverness's lead.
There was to be no way back for the Paisley men and when goalkeeper Ryan Esson desperately clawed away a powerful downward header from Thompson in injury-time time, the home side's fate was sealed.