Not so long ago, although it now feels like a galaxy far, far away, Nico Rosberg and Lewis Hamilton were childhood chums travelling together to karting circuits, dreaming about a career in motor sports.
Formula One (F1) threw that bond out of the window. And in a frank admission, Rosberg said that while both feuding Mercedes drivers respect each other, their friendship had cooled. And no quarter will be given when they continue their high-speed duel in the Formula One Singapore Airlines Singapore Grand Prix this weekend.
In an engagement that lasted more than an hour yesterday evening, Rosberg was friendly and obliged all wefie and autograph requests at UBS' office in Raffles Quay.
He was there to meet and greet 10 winners of a contest jointly organised by The Straits Times and the financial services company.
The German then proceeded to attend a panel discussion on artificial intelligence entitled Decision Making: Man vs Machine.
But the desire to compete, to be the F1 world champion, is the cold logic Rosberg applies when it comes to his relationship with his team-mate Hamilton.
FRIEND OR FOE?
It's completely normal and understandable for me because we are both extremely competitive and nothing was different when we were in go-karts.
NICO ROSBERG, on his rivalry with Mercedes team-mate Lewis Hamilton.
He explained: "It's (his rivalry with Hamilton) not something that I think about much, it doesn't weigh on me in any way. It's completely normal and understandable for me because we are both extremely competitive and nothing was different when we were in go-karts.
"In go-karts, (it was) the same - we're so extremely competitive. When we went out for dinner, it would be how many pizzas we could eat. The competition never ends but we could be friends at the same time because it was a lot less media, sponsors, interest, talking... it was just us and a few mechanics.
"So it was a lot more simple and it was possible to be friends but now there's so much more to it."
But with just two points separating drivers' championship leader Hamilton (250) and Rosberg (248), the stakes are high. Already, the two drivers have crashed into each other twice this season.
Rosberg continued: "But we have this respect under everything that still remains. So I respect him and he respects me even if sometimes we get some heated moments and we crash into each other.
"It can be very, very intense but it's OK. We get over it, we keep racing and it's neutral between us and may the best one win."
Although much has been made of Red Bull's strength in street circuits, where their downforce compensates for their lack of power against the Mercedes, Rosberg has won three of the four street races (Melbourne, Baku and Sochi) this year while Hamilton triumphed in Monaco this year.
This season has also been a breakthrough of sorts for the German as he clocked up maiden wins in the Bahrain, Russian, European, Belgian and Italian grands prix.
But the 31-year-old still dreads the heat, humidity and twisting tarmac of 61 laps over the Marina Bay Street Circuit.
He said: "Singapore is very unusual. Last year, we got destroyed by Red Bull and Ferrari. They were 1.5 seconds quicker during qualifying and it's huge. You just can't change like that overnight.
"It's not the easiest weekend but it is an amazing event. They even put metal plates under our cars so that it makes sparks that you can see in the night and it looks cool.
"But I don't like the circuit because it is one of the toughest races of the year. I feel horrible from all the sweating... I am dressed up like I'm going for skiing but I lose up to 4kg (in water) in two hours."
While he is not rating himself as the favourite for the Singapore night race, he is impressed with a particular Singaporean.
Heaping praise on swimmer Joseph Schooling, who won the Republic's first Olympic gold medal in last month's Rio Games and pipped Michael Phelps in the American's last individual race, Rosberg said: "Awesome result, that was incredible, beating the legend!
"That was wow... you must be very proud. That's really an incredible story. What an amazing job he did and he destroyed them.
"It was really impressive and I was watching that."