Benzema has only scored twice in 15 La Liga appearances this season, while he has competed the full 90 minutes on just five occasions in Spain's top flight.
Papin has suggested that Real Madrid, who are 19 points off league leaders Barcelona, are paying the price for not signing "a number nine" to work alongside Benzema.
"Personally, I would have signed a number nine, but that's my point of few. I think Madrid needed to strengthen what they've got there," Papin told AS.
"The perfect example is Benzema - he scored a lot of goals and now nothing's coming off for him. He doesn't even look dangerous, which is very strange.
"But nobody is better placed than [Zinedine] Zidane to judge what the team needs. He knows the group and has confidence in those players. He wasn't wrong over the last two seasons so we have to trust him. I respect Zidane a lot. What he has done is great."