The former Manchester United striker has failed to command a regular place under new boss David Moyes or his predecessor Slaven Bilic.
National newspaper reports have linked Carroll with a move to Premier League defending champions Chelsea while Hernandez has struggled for game time since Moyes' arrival in November.
"The form of Marko Arnautovic and Michail Antonio, at the start, has probably made it hard".
The 54-year-old told BBC's Football Focus: "I've got an idea in my head how I want it to look".
"Were not sure yet but if it is the latter - and that would be a real shame - we will need to go out to try to make a suitable signing this month because we will need someone who plays down that right-hand side". So ideally, we strengthen.
The Hammers face a crucial run of winnable fixtures which could go some way to securing their Premier League safety.
The quartet have notched a paltry 11 Premier League goals between them so far this season. "It would take an bad lot of money to prise them out".
Moyes added: "When I joined Javier was injured and we'd to go with Marko and Michail up front and they have both done well". Mexico fans anxious when Moyes took over after his history with Chicharito at Manchester United when he left the forward on the bench during the majority of the 2013-14 season.
"Chicharito is a really good player and his finishing ability is as good as there is anywhere". He thrives on balls in the box. "You would be hard pushed to say he would necessarily be playing ahead of the two other players I mentioned at the moment".
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