There was speculation Martinez had suffered a serious Achilles injury which would end his season.
"I cannot tell what it is, but is not an Achilles," the Dutchman told reporters. "I have spoken with him and he is okay and he is calm."
The draw with Sevilla was not the only disappointment as Martinez joined a list of injured players including striker Marcus Rashford, defender Luke Shaw and Martinez's fellow centre back Raphael Varane who had to be replaced at half-time.
"I think (it is) an injury (that means) he will not play on Sunday," Ten Hag added, "I cannot say what the diagnosis (is). I prefer to wait and to know what it is."