London - Sebastian Vettel and Charles Leclerc are a "potentially explosive combination" who need to be handled with care by Ferrari, the team's former technical director Ross Brawn said on Tuesday.
Brawn, now Formula One's managing director for motorsport, was the strategic mastermind through a golden era for the Italian team when Michael Schumacher racked up five championships in a row from 2000 to 2004, adding to two won with Benetton.
Vettel, 32, is a four-times world champion, but the German has been outperformed this season by 21-year-old rising star Charles Leclerc, who has taken six pole positions and two victories.
The pair stood out in last Sunday's Russian Grand Prix for testy exchanges over the radio after Ferrari tried to swap their positions in a failed bid to engineer a one-two finish.
Mercedes won the race one-two instead, with five times champion Lewis Hamilton leading Valtteri Bottas, to end Ferrari's run of three wins in a row.