"It's a maybe. There will be plenty of interest in him, and if his contract was terminated I don't think he can play before January," Keane told the East Anglian Times.
"But like any player potentially becoming available who can improve us I am keeping tabs on the Campbell situation."
Keane admits he was not shocked by Campbell's decision to walk out on Notts County after signing a five-year deal at Meadow Lane.
"I wasn't really surprised," he added. "I admire people who are brave enough to make a decision.
"There are a lot of players up and down the country who are happy to sit on their contracts and pick up the money."