A third place finish will guarantee the title for Rosberg, but Surer thinks that the German should ditch a conservative approach and go all out for the win.
"Rosberg can only lose," Surer said of Rosberg's title chances.
"A second or third is not a problem for the Mercedes, but if he drives too carefully, someone might get in the way. This is almost worse than going to the limit," he told the German broadcaster Sky.
Surer added: "If he can, Nico should try to win from pole position. That way, he won't get caught up in a fight with a Ferrari or a Red Bull. And if Rosberg is to be world champion, it would also be better for his image.
"Lewis, on the other hand, can only drive with the motto 'All or nothing'," he said.
Surer also feels that Rosberg will be a better champion for Mercedes.
"For me, Nico Rosberg is the better champion for Mercedes," he said. "Internationally, Hamilton has the bigger name, but Nico has an image that fits easily with Mercedes. With his gold chains, you wonder about that with Hamilton."
Bahrain International Circuit - Winter testing