The 30-year-old has fallen out of favour at Goodison Park this season under the former Wigan Athletic boss, with both of his appearances coming into the League Cup.
Although Martinez admits that he would like to see the Netherlands international - whose contract expires in the summer - remain at the club, the Spaniard said that he would "help" the defender in his bid to seek pastures new.
"Johnny is a top footballer and we can understand if he doesn't play many minutes we will try to see if we can help him in January," he told reporters.
"But ideally I would like Johnny to start playing and have a big role on the pitch as much as he has off it.
"We all want Johnny to play and participate on the pitch but that is something we will have to assess over the next few weeks."
Serie A outfit Fiorentina are among those reportedly keen on the former Ajax centre-half.
The Toffees sit fifth in the Premier League table, level on points with local rivals Liverpool.