"I think the business done in January will be minimal," Allardyce told reporters. "It's too small a window to find what you need, which are players of greater quality."
"At the moment we're trying to ... introduce a solidarity to our squad so, to introduce another four or five players, might actually cause more harm than good."
Yet Allardyce refused to rule out selling former England international Defoe.
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"At the end of the day, whatever happens, happens," he said, when asked if he would be willing to countenance the sale of the player who grabbed the winner in their 1-0 Premier League victory over Crystal Palace at the weekend.
"If I ring an opposition manager or football club and I want one of their players, what determines if that player is available or isn't available changes day by day.
"There's no definite players that we know of going out from here. In terms of a specific player, we don't know," he added.
Sunderland, whose win against Palace lifted them to third-from-bottom in the table, host 11th-placed Stoke City on Saturday.
(Reporting by Simon Jennings in Bengaluru. Editing by Patrick Johnston)
