Lewis Hamilton and Valtteri Bottas, who qualified second and fourth respectively, both used the medium compound tyre for their flying-laps in Q2, meaning they will have to start the race on that compound.
Ferrari drivers Charles Leclerc, who is on pole and Sebastian Vettel, who starts third, will both start on the soft compound at Sochi Autodrom. Binotto said Ferrari rejected a similar tyre strategy to Mercedes.
"That's surprising to us, their choice," Binotto said to Sky Sports F1. "That's something we were considering to be honest. I think we need to try to understand why they did that choice.
"Certainly we believe that the soft tyre's got a grip advantage at the start. The start will be key tomorrow. But maybe that's the right they did. Different strategies may do something interesting for the race for the fans to see."
Binotto also spoke on Leclerc, who is on pole for the fourth successive race: "He surprised me how fast he is at first. I think he's really very fast and that's something which is important for a team when you can count on a driver who is so fast. That's the most you may have."