Forestieri started for the Owls on Boxing Day, as they squeezed past Birmingham City, but he was omitted from the Owls’ line-up at the Riverside Stadium.
His exclusion was a controversial one, but Carvalhal claims that the Argentine forward asked for a break.
"Fernando came to talk to me and said 'I'm not ready to play 90 minutes because I don't feel energy'," Carvalhal said.
"He said 'If you need me during the match I am ready'."
With Forestieri on the bench, Wednesday didn’t show their usual attacking class in the North East and they fell to a 1-0 defeat against Middlesbrough.
Aitor Karanka’s side took the lead in the first minute through Christian Stuani, and they never looked back, as they claimed the three points.
Middlesbrough have now not let in a goal in over 10 hours of Championship football.
Wednesday, meanwhile, are in seventh place in the standings, after their defeat on Teeside.
The Owls’ next match comes against Fulham on Saturday, and Forestieri looks set to start in that fixture.