The Toffees lost 2-1 at Norwich on Saturday following a late rally by the home team in a match they should have long put to bed after taking a first-half lead through Leon Osman.
Naismith said: "The squad haven't moaned about tiredness, it is not something we've spoken about.
"We're professionals and you have to go out and do your job. We work every day and we work at a good level so the boys are definitely fit enough. I don't think they're tired at all."
Naismith added: "We've maybe not been playing as well as we did at the start of the season but we've ground out some results."