The 24-year-old, signed from Marseille for £2.5million this summer, has yet to feature in the Premier League and made his only appearance to date in the Carling Cup clash with Swindon last month.
But the former France Under-21 international could be involved at Goodison Park - either in his most natural position of centre-half, or at full-back.
McCarthy told the club's official website: "Ronald has looked great in training - it might be that he's ready to play against Everton.
"When he came here, it just didn't happen for him and he didn't look as sharp as he'd have wanted. He wasn't ready to play, but he's looking a hell of a lot better now. He's training brilliantly and he looks a far, far better player. He's now looking like the player I bought when I signed him.
"The players in central defence haven't done badly but, as I said to them, 'it doesn't matter how well people are doing, we can't keep losing games'. We've got a squad of players and Zubar has played everywhere across the back four when he was at Marseille."