The 31-year-old joined the Owls in the latter stages of the summer transfer window, but would go on to make just four appearances at Hillsborough before returning to the Welsh capital in January.
Since then, he has established himself as a mainstay of McCarthy’s resurgent Bluebirds side, and hasn’t missed a game since he came back into the starting XI against Barnsley on January 27th.
Reflecting on the decision to allow Flint to go out on loan prior to him taking over at the club, the ex-Republic of Ireland manager admitted that he was left a little dumbfounded by the call.
He said: “I’m really pleased for Aden.
"I’ve always really rated him as a centre-back and I was surprised to hear he had gone out of our club on loan.
"He’s been fantastic for me.
"I had a word with him the first week I was in and he has been brilliant. I am amazed at his resilience, how he has come back."
Since returning to Cardiff, Flint has registered the third-highest average match rating of any player in the Bluebirds’ squad, as per stats-based site Whoscored.com.
Elsewhere, Carlton Palmer has cast doubts over whether or not Carlos Carvalhal will one day return to Hillsborough as manager.
The ex-Owls boss, who spent two years with the Owls, recently hinted that he would like to have a second stint in England, and even implied that he could see himself back in the dugout at Wednesday.
But Palmer is less convinced.
Speaking to Football Fancast, he said: “Well, Carlos did well, I mean, did really well.
"I mean, they went to the play-off final with Carlos and then into the play-offs [the following season].
"So, yeah, never say never. But I always think once you’ve moved on, you’ve moved on. Do you know what I mean?
"Even Sir Alex Ferguson going back to Manchester United wouldn’t be the same. I think once you’ve moved on, you’ve moved on.”
Carvalhal currently manages Portuguese side SC Braga.
We’ve gathered the rest of today’s Championship speculation below:
1. Southampton want Bristol City trio
Daniel Bentley, Tyreeq Bakinson and Antoine Semenyo are all on the radar of Southampton, with Wolves also making regular checks on Bristol City this season. (Bristol Post) (Photo by Marc Atkins/Getty Images) Photo: Marc Atkins
2. McCarthy opens up on Flint exit
Mick McCarthy has express his surprise that Cardiff City defender Aden Flint was ever allowed to leave the club to go out on loan to Sheffield Wednesday. (The Star) (Photo by Alex Burstow/Getty Images) Photo: Alex Burstow
3. Bristol City keen on Pritchard
Bristol City hold an interest in Huddersfield Town midfielder Alex Pritchard ahead of the summer. (Bristol Live) (Photo by Tony Marshall/Getty Images) Photo: Tony Marshall
4. Barnsley forced to make MacDonald payout
Barnsley have been forced to pay Hull City a fee in the region of £1m over an ongoing saga involving the transfer of Angus MacDonald. (Yorkshire Post) (Photo by Alex Pantling/Getty Images) Photo: Alex Pantling