The 31-year-old South Africa international is reportedly interested in leaving the club, due to a lack of first-team action.
Allardyce told BBC World Service Sport: “At his age I’d understand if he wants to play first-team football and at the moment he can’t get it here.
“If he wants to get it somewhere else I’d understand that.”
“There is a price to be met if someone wants to buy Benni McCarthy,” he continued.
“If the club is happy with that price we will go to Benni and say we’ve accepted a deal from a certain club. Now it’s up to you to see if you can sort your side of it out.
“But we would have to have a replacement for him to allow it develop in to him being transferred.”
He added: “Benni wants to play football. For me last year he was excellent particularly at home in our plight to climb out of the relegation zone.
“I was looking forward to the start of the season with him but all of a sudden we put David Dunn in at Gillingham away in the hole behind a front man.
“He played so wonderfully well in that game that we have continued that position for him in the first team. He has grasped that position so well that he is our top, top player at this moment in time.”
