BUDAPEST, Hungary (AP) — When Charles Leclerc retired moments after the start of Sunday's Hungarian Grand Prix, it was hard to picture him as Formula One's rising star.

But Leclerc, in his debut season with Sauber after progressing through the prestigious Ferrari academy, is touted as a future F1 champion.

So is Max Verstappen, who retired a few laps later when his Red Bull car sustained an engine problem.

The two 20-year-olds are more likely to be topping the leaderboard than retiring in years to come, having been rivals previously in karting.

"Honestly, it was quite tense during our karting years. We say 'Hello' to each other in the paddock (now), but we're not the best friends in the world," Leclerc told The Associated Press in an interview. "But the aggression (Verstappen's) shown in F1 is more or less the same he had in karting, which also makes him a special driver."

While Verstappen holds impressive records as the youngest to win a race and qualify in the top two — at just 18 — Leclerc is starting out.

"Every time a young driver comes into F1, the finger's pointed at him over his age," Leclerc told the AP at the Sauber team motorhome during the Hungarian GP. "I don't think that's right. You should be judged on your performances, not how long you've been around."

Expectation levels will rise further if Leclerc, who is from Monaco, continues driving with the skill he has shown in several races this season. Five top-10 finishes, with a best of sixth in Azerbaijan back in April, means he is regularly scoring points with arguably the slowest car.

He does not see age as relevant, especially after France won the World Cup with a youthful squad featuring jet-heeled 19-year-old forward Kylian Mbappe.

Mbappe's moto is that if you're good enough, you're old enough. Asked if he agrees, Leclerc answers quickly.

"Yes, completely," he said. "I don't even think about (age), I don't think I ever have."

Leclerc watched his first Monaco GP in a family apartment overlooking the track when just four years old.

"I remember we were playing with toy cars while watching the race," Leclerc said. "I was a big supporter of the red car, the Ferrari."

Remarkably, he had first tested his driving skills at 3 1/2. It was on a karting track owned by the father of Jules Bianchi, the promising French driver who died in July 2015 at the age of 25, after fighting several months to recover from head injuries sustained at the Japanese GP.

Bianchi's father, Philippe, was a close friend of Leclerc's father, Herve — a former F3 racer.

But it was Philippe towing young Charles around the track.

"Strangely, I remember my first lap. We'd attached a rope to his kart, to see if I had the right reflexes, whether to turn left or right," Leclerc recalls with impressive detail. "After the first lap, we took the rope off and I continued on my own."

A prodigious talent was unleashed.

Although several years apart, Leclerc grew close to Bianchi, who lived in nearby Nice. Bianchi mentored Leclerc in junior karting. Leclerc won the 2009 French championship and later took on Verstappen, Pierre Gasly and Esteban Ocon — who are all now promising F1 drivers.

As Leclerc's reputation rose, his friend — once a young prodigy himself — helped him.

"Jules often came to races. He also taught me not to let things get to me, because he noticed that I did," Leclerc said. "Seven or eight years ago, my biggest weakness was my mentality. I was pretty emotional but I've worked really hard on that and now it is one of my strengths."

Leclerc speaks with admirable emotional control about Bianchi, whose death affected him deeply. He remembers how Bianchi helped his career — and perhaps even saved it — by intervening on his behalf in 2010. Bianchi spoke to his own manager — Nicolas Todt, the son of FIA president Jean Todt — and persuaded him to help Leclerc.

"We really wanted to make the (next) step to international karting, but the budgets were multiplied by 10 and it was just no longer possible," Leclerc said. "Jules went to see Nicolas and said 'Have a look at Charles, he might interest you. Because if there's no one to help him at the end of the year, he might stop.'"

Two years after losing his close friend, Leclerc lost his father.

It was shortly before the F2 GP in Baku and Leclerc did not pull out. Instead, he took pole position and won.

"I didn't think I could do a good performance," Leclerc remembers. "But I was able to try to get the best result possible for him."

Leclerc won last year's F2 championship in style, and at the first attempt, fast-tracking him into F1.

With his boyish features and calm exterior, Leclerc's inner strength is not visible. How he talks openly of his losses is a better example.

"Losing Jules and then (briefly pausing) my father made me much stronger mentally," Leclerc said. "When you go to a race having just lost your father, it's not easy. It gave me a certain autonomy which helps me now."

A year before his death, Bianchi finished ninth at the Monaco GP for the Manor Racing team. With the weakest car on the most difficult track for overtaking in F1, it was a phenomenal achievement and saw him touted as a future Ferrari driver.

That mantle now rests with Leclerc, who will always remember who helped him.

"Jules helped me a lot with all of his advice. My father, well he helped me with everything," Leclerc said. "From the start he was my biggest supporter and taught me a lot about his experience as a driver. Without them I wouldn't be here, and I don't want people to forget them."

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More AP Auto Racing: http://racing.ap.org

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Jerome Pugmire is at www.twitter.com/jeromepugmire