Barkley suffered medial ligament damage in training before the start of the new Premier League season, ruling him out of Everton's campaign so far.
However, Martinez says the England international is showing good progress and could be back in the fold sooner than initially expected.
"Ross is progressing well but is still receiving treatment," he said. "He's in week four now and is probably a couple of weeks ahead of where he should be.
"But he's still halfway through his recovery period."
Like most top-flight clubs, Everton have welcomed back a host of international stars this week, and Martinez is delighted with the overall condition of his squad.
"Everyone has come back in a really good frame of mind," he added. "They all had really good experiences.
"We had up to 12 or 13 players going away on international duty and you always feel that the players are a little bit out of your control.
"You hope that they come back strong and ready to participate with a real confident look about their player and I think that's exactly what's happened.
"Steven Pienaar, Arouna Kone, Bryan Oviedo and Romelu Lukaku joined the group for training today which has been very positive.
"Leon Osman and Samuel Eto'o picked up a couple of knocks in the last two games and we're going to assess them over the next 48 hours.
"But everyone else is fit and available for the next period. Not just the game at the weekend, but I think in the period of so many games coming up, it's going to be really important for the squad to be ready and available."