The Dutch defender was forced off in the second half of the 3-2 defeat to the Swans after going down in a strong challenge and it is believed that perhaps he may have a break whilst Jean Beausejour will miss the final two matches and the FA Cup final on Saturday with a leg injury of his own.
"We will check Ronnie tomorrow, but it seems it is a broken leg," said Martinez.
"He couldn't put any weight on it, so he will need a scan tomorrow to find out exactly what it is."
"Jean has a tear in his right leg,â he added.
"It will be difficult for him to be back before the season ends."