The South African midfielder sustained a leg problem last week, forcing him to miss Saturday's 1-0 win over Chelsea, and Martinez has revealed that he could spend some time on the sidelines.
But the Toffees boss had some better news for striker Arouna Kone who is set to return from a knee injury.
Steven Pienaar is going to be a little bit longer - it's a grade one soft tissue problem. But Arouna Kone shouldn't be too long," Martinez told the club's official website.
It is believed that Pienaar will miss around a month after suffering the injury in training.