Charles Leclerc's rise at Ferrari has put Sebastian Vettel in a challenging and difficult situation for the 2020 season, according to Nico Rosberg.
Rosberg, the only man apart from Lewis Hamilton to win a Formula One world championship since the last of Vettel's four titles in 2013, believes his fellow German's struggles pre-date the 2019 campaign.
But the sensational debut Ferrari season from Leclerc has brought the future of Vettel into the spotlight, with his contract having only a year left to run.
Leclerc earned seven pole positions and two race wins last year to finish ahead of his more experienced team-mate, who has just one victory in his last 29 attempts, in the drivers' standings.
Rosberg feels if anyone can bounce back from such a predicament it is a driver of Vettel's calibre, but he acknowledged how tough the situation is for the 32-year-old.
"We must not forget that he also had a very tricky 2018, so it is not just last year, it has been a string of years now," Rosberg, Heineken's 'When You Drive, Never Drink' ambassador, told Stats Perform.
"It's not an easy situation for him because he is such a great driver.
"He is also one of the best of all time, but now he is finding himself in a very challenging situation with an unbelievably fast young team-mate, who is also getting more and more support internally from his team.
"So it is really a difficult one for Sebastian, but if one guy can do it and bounce back from that, then it is him, because he has all the confidence, all the experience, he has the speed."
Rosberg feels one of the most significant storylines to watch this season will be how Ferrari manage the rivalry between their two drivers.
Tension over team strategy developed between them over the course of 2019, culminating in a Brazil collision that caused a double retirement.
"It is so exciting to see how that is going to play out internally," added Rosberg.
"It is going to be hugely challenging for Ferrari to manage that because last year it was much easier. It was very clear - Sebastian was the number one and Charles was the number-two driver.
"As soon as that started to be debated internally, that is when the problems started, around Monza. Both will be equal number-ones in the team going into the season and that is going to be super interesting to watch."
Looking ahead to this year's title race, Rosberg - the 2016 world champion - tipped Leclerc and Max Verstappen to challenge strongly, adding: "The biggest threat [to Hamilton] really depends on the cars.
"I believe that Red Bull and Ferrari really might step it up this year and go on level playing terms with Mercedes. That would be amazing, we would be glued to the TV, it would be so cool – and it is possible.
"If that's the case, then the biggest threats - looking at last year - will be Verstappen and Leclerc, but you definitely cannot count out [Valtteri] Bottas and Vettel either."
Rosberg was speaking following the launch of Heineken's 'When You Drive, Never Drink' campaign, for which he has starred in a TV commercial alongside his father, fellow F1 world champion Keke Rosberg.
"It was such a huge pleasure to do the filming with my dad," said Nico Rosberg, who has been a road safety ambassador for several years.
"And then integrated into that we have the total abstinence message to help save lives, because total abstinence is the only way to do it. One drink is already one drink too much [if you are driving].
"The latest campaign conveys a really powerful message that, regardless of whether you’re a professional driver or not, abstinence behind the wheel is the only option."