It was reported last week that the midfielder could be sidelined for up to five months after suffering ligament damage in training.
However, Martinez has suggested that the England international could be back in action sooner than that.
"His knee has reacted really well to treatment," he told the club's official website. "I don't know where the figure of five months came from but obviously the extent of the injury is a little unsure at the moment because we don't know how the next two weeks are going to develop."
Barkley recently signed a four-year contract extension with the Premier League club.