But the Owls' head coach has already masterminded one victory against United this season, and believes his players will be full of confidence after winning their South Yorkshire derby against Rotherham this week.
Glenn Loovens' goal was enough for an impressive Wednesday outfit to claim the points at St. James' Park on Boxing Day, but Carvalhal told his club's official website: "Before the season, everybody agreed that Newcastle are the number one candidate for promotion.
"When you reach this stage of the season and they are top, they are the best in the division, not just in theory but in practice.
"When you play the team that is first in the table, it’s the most difficult game of the season for sure.
"It's a big challenge to us, we respect them a lot, they have plenty of quality, quality individuals, a collective quality with a good manager.
"But we are Sheffield Wednesday, we play in Hillsborough and we will be ready to the game, understanding that we are playing against the strongest side of the competition. To be near and near our best level is what we need that to achieve the points."
Carvalhal is hoping to welcome Kieran Lee and Fernando Forestieri back from injury for Saturday's game.
And he insisted: "We don't look to the last time we played Newcastle, we win confidence from the last game we played on Tuesday.
"The confidence to the players comes when you win, when the team wins, this is the best.
"We needed the victory in the last game and the signals we gave were important to us."