Carvalhal has made an impact since arriving at the Liberty Stadium just a few days after departing the Owls on Christmas Eve, with Swansea beating both Liverpool and Arsenal to drag themselves out of the Premier League relegation zone.
"It is important if it is the best result in the history (of the club), but the most important thing is the attitude of the players that made all the difference", Carvalhal said.
"The team they put out in the initial tie was strong and they played well, moved the ball well but we looked comfortable and I didn't have too many saves to make".
First-half braces from Tammy Abraham and Nathan Dyer, as well as second-half efforts from Kyle Naughton, Wayne Routledge, Tom Carroll and debutant Daniel James, saw Swansea cruise towards a last-16 tie at Hillsborough.
"I don't think they deserved to be 8-1, but it is one of those games where their finishing was Premier League standard", the former West Ham United captain told BBC Sport.
The reward for Carvalhal is a meeting with the club that fired him in December, second-tier Sheffield Wednesday.
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"I feel that I will be back home", Carvalhal said.
"I consider it my home the last two season and a half".
"Some people were not happy but when they put emotion aside they know we gave everything to the club".
Abraham, now with scored seven goals in all competitions, will hope to get another opportunity when the south Wales outfit host Burnley in Saturday's English Premier League fixture. It will be a special game for me because I was there not a long time ago but at the same time it is the cup and we will try to do our best again.
Swansea opened the scoring after 18 minutes as Luciano Narsingh played a one-two to skip clear down the right, delivering a near-post cross that Abraham turned home for his first goal since October. He stated that County need to stick to their game plan and that "if we can get on the end of a set play hopefully we can capitalise on that".