Ayew was handed a three-match suspension last month after picking a direct red card just 10 minutes into the Swans scoreless draw against Huddersfield following a reckless challenge on Jonathan Hogg.
The 26-year-old forward served out the last of the three games last weekend when the Swans played out a 1-1 stalemate with West Bromwich Albion at the Hawthorns.
"To me he is one of the best attackers in the Premier League, a fantastic addition to us," said Carvalhal.
The Portuguese trainer also confirmed there has been no contact from Man United for defender Alfie Mawson, despite report linking him with a move to Old Trafford.
Ayew, who has been joined at Swansea by his brother Andre, has scored six of his ten goals this season since Carvalhal arrived just after Christmas, having struggled for consistency before then.
Asked what he had done to improve Ayew's form ahead of his return from a three-game ban, Carvalhal joked: "I don't know how good he was before. I kicked him in the neck and said 'let's go!'
"I put him in the correct position and gave him confidence to play… that's what we did to him."
"It is my surprise people were being negative about him before I arrived."
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