The Owls are ninth in the Championship after picking up just one point in their last three games.
Wednesday signed midfielders Almen Abdi, Adam Reach, David Jones and Will Buckley and striker Steven Fletcher in the summer.
"We are giving time to them. I still believe we have very good players," Carvalhal told BBC Radio Sheffield.
"I don't want to criticise and I'm not disappointed in anybody, but I expected a little more from them.
"Some of them have had problems, like Fletcher, who has missed some games from kicks to the head.
"We are in the first part of the season and I think with more chances and the team in a better position then the players will do better in the future."
Swiss international Abdi, 30, joined from Premier League side Watford for a reported fee of £3m in July.
He has not started a game since 19 October, but Carvalhal says he will not be allowed to leave on loan in January.
"My job is to choose the players that are the best to win a game from the way they are performing during the week," the Portuguese said.
"We don't consider Almen leaving at all. We believe in him. We want him to perform well and so does he."
Sheffield Wednesday boss Carlos Carvalhal has admitted he "expected a little more" from his summer signings.