Fletcher suffered a foot injury early on in Saturday's 2-1 win at home to Stoke while Doyle missed the game with a calf injury.
However, both should be fit for Saturday's trip to Everton.
McCarthy told the Express and Star: "I think Fletcher will be alright, it's just some bruising on the bone. He got a kick on the instep and asked us to give him five minutes in the second half.
"Then a minute afterwards he smashed the ball from 25 yards. That's one way to test it out I suppose! He realised it wasn't going to be any good from there and it was sad he had to come off.
"Doyle will be fit for next Saturday. He fits right into my plans at the moment, don't worry about that."