Vettel and Leclerc were partnered together at the Scuderia outfit in 2019, with tensions present throughout the year amid a number of team order spats.
At the Brazilian Grand Prix, the duo came together in the final stages of the race, sending both drivers out of the race.
Leclerc ended up ahead of Vettel in the drivers' championship, scoring seven pole positions and two victories throughout the year, his first at Ferrari.
Berger admits he was encouraged by Vettel's performances in the final part of the season and believes experience may fortune him this year.
"In the last third of the season, Vettel showed that he can beat Leclerc very well," Berger told Auto Motor und Sport. "Unquestionably, Leclerc has the future ahead of him and Sebastian is in the last stage of his career.
"But he has so much experience, has been world champion four times, and at Ferrari for five years. From this he can balance out the boy's bravery.
"It will be an interesting duel," Berger added. "But I don't dare to predict the outcome."
Ferrari recently committed its future to Leclerc, who signed a contract extension that keeps him at the team until at least the end of 2024.
Vettel's contract at Ferrari expires at the end of the 2020 campaign, with question marks lingering over his future at the team and in F1.
"We don't know if it's a decisive year for him personally," Berger said. "Will he do his last year and want a good retirement? Does he want to take on Leclerc?
"Clearly Leclerc is a tough nut to crack, but that's always the case when you drive for Ferrari, Mercedes or Red Bull.
"It always was that, at the top teams, there are two alpha animals who butt heads until one remains. When I went to McLaren, it was Senna. You can't run away from it," Berger concluded.
Bahrain International Circuit - Winter testing