The West Ham striker, on-loan from Liverpool, has scored six goals in his last 11 appearances and proved more than a handful for champions-elect Manchester United in midweek.
United boss Sir Alex Ferguson felt the Hammers' front man should have been sent off for flattening goalkeeper David de Gea in their 2-2 draw at Upton Park.
But Martinez insists players have to use whatever strengths they have to their own advantage and will be preparing his defenders for more of the same.
"He is a potent threat and he's always been a threat," said the Latics manager.
"We have seen him at two previous clubs show the same power and strength and he did it for England at the Euros and was very impressive so I don't think it is a surprise to anyone."
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- Manchester United