Despite finishing runner-up to Sebastian Vettel three times, Fernando Alonso rates Michael Schumacher as the strongest rival he has faced in F1.
Alonso entered Formula 1 in 2001, the second year of Schumacher's five year domination.
Four years later, the then Renault driver would become the one to end Schumacher's reign as he claimed the Drivers' title in 2005 and again in 2006.
Since then Alonso has go on to battle the likes of Lewis Hamilton, Kimi Raikkonen and Vettel. But it is Schumacher who he rates as the fiercest of them all.
"The strongest in Formula 1 was Michael," Alonso told the Ferrari website when asked about his past rivals.
"In the years when I was staring in Formula 1, in 2001 he dominated and he did so up until 2005 and he was on another level.
"With him it was never easy.
"Then I got the opportunity to race against him on equal terms for a few years and he was always able to do something special, something more than you were expecting, or maybe more than the car was capable of.
"So you always had to keep an eye on him."
As for the team-mates he has come up against, the double World Champion singled out Jarno Trulli for his qualifying ability and Giancarlo Fisichella as a "complete" driver.
Asked who has been his strongest team-mate, he said: "It's a difficult question.
"They were all different, all had strong points and some not so strong, so I had a heard time with all of them in terms of performance and you had to give your maximum because they were ultra competitive.
"I remember Trulli, Trulli's qualifying ability was the best I've ever come across among all my team-mates.
"Then there was 'Fisico' Fisichella, for two years in Renault, when we won the Constructors' titles and he was always on it, in every race, in all conditions, a really complete driver.
"There was Massa and now Kimi and, even in the past there were kids in go-karts who were super, so it's not easy to choose one.
"All of them helped me, and I learned a lot from them to do with various aspects, but they all had something special."
As for his friendships with his team-mates and his rivals, a "friendly relationship" is probably a better way of putting it.
"Yes there can be [friendship] but definitely not in the real sense, not in the way you have friends outside Formula 1 or friends from school that you have known for a very long time.
"In Formula 1 the friendship isn't forced, but it's based on spending 300 days a year together and in the end you begin to share things that are not just related to work but are also personal and that creates a friendly relationship."