Latics boss Martinez insists his side must keep an eye on the Hammers' other stars, who also have the ability to plunge them further into trouble.
He said: "Andy has always been a threat. We saw at his two previous clubs his power and his strength - and he showed that for England at the Euros.
"I don't think he has surprised anyone with what he is doing now.
"But if we focus too much on one player, then we will leave space and room for others.
"West Ham are more than being a one-man team and we will be very aware of that."