The Republic of Ireland star has been missed since his injury late last year but is now expected to be fit to face Crystal Palace next weekend.
Veteran French defender Sylvain Distin is also on his way to recovery.
“Sylvain Distin and James McCarthy are really progressing a lot in this warm weather and that’s really positive news,” said Martinez.
“They have both joined the group in training and have come through really well.
“I see James as being fully fit now but we will assess everybody before the Crystal Palace game.
“This week has allowed James to build up his fitness levels and I do expect him to be fully fit and ready for Crystal Palace.”