Mexico City - Alain Prost has warned Ferrari that they must control their embattled drivers or risk handing another world title double to Mercedes next season.
The four-time world champion, who was embroiled in one of Formula One's fiercest in-team rivalries when he and Ayrton Senna were team-mates at McLaren in the late 1980s, said Ferrari faced a "complicated situation of management".
The Frenchman said he could foresee the battles between four-time champion and team leader Sebastian Vettel and young pretender Charles Leclerc costing them the title and handing it to Mercedes again.
"With his experience, Vettel was considered the number one in the team, so it;s hard to manage that," he told BFM TV. "I think it's going to be difficult, especially next year.
"I think Ferrari will be strong next year and they will have to deal with the fight between Charles and Sebastian. If the car is good and they are both fighting over the title, that could give it to Mercedes."
Ferrari have shown outstanding speed and form since Formula One's European summer break in August, taking five successive pole positions and securing three victories. Leclerc has won twice and Vettel once.
But their bid for glory has been hampered by their drivers' rivalry as shown in Russia, where Vettel ignored team orders, and Japan, where he took pole, but had a bad start and Leclerc collided with Max Verstappen.
Prost added that Monegasque prodigy Leclerc was "already a big star" who has "adapted very quickly to almost number-one status in a team like Ferrari that never took a young driver before."