Everton have won four of their last five matches in all competitions.
Martinez has not been able to name McCarthy and Barry alongside each other in midfield as often as he would have liked this season, due to injury.
McCarthy only played once between November and January, but the Republic of Ireland international’s return has considerably improved Everton’s performances.
The Toffees have won four of their last five matches, and Martinez admits that Everton look a much stronger team when their first choice midfield duo are available.
“They give a totally different balance and look to the side and that has been very important in the last five games," Martinez said. "The team looks very solid now and we have missed James when he has been out.”
Muhamed Besic was generally picked to cover for McCarthy, but he did not manage to offer Everton’s defence as much protection as the former Wigan Athletic man.
The Toffees have so much attacking quality, that having two disciplined midfielders is crucial for their style to be effective.
Everton’s most recent match ended in a 2-0 triumph over Bournemouth in the FA Cup, with Ross Barkley and Romelu Lukaku scoring the goals which helped the Merseyside club to progress.
Everton will now meet Chelsea in the quarter-finals in March, as they look to book their place at Wembley.