Despite driving for the same team, Lewis Hamilton and Nico Rosberg were constantly at each other's throats for three years between 2013 and 2016.
The pair battled it out to win the Driver's Championship last year, with the German just pipping his teammate to the title in the final race of the season.
Just five days later, Rosberg announced his retirement, and would not race in F1 again.
His decision ended Mercedes' three years of domination at the top of the sport. Although they've replaced him with the impressive Valtteri Bottas, it seems they've got some competition at the top.
Ferrari are just eight points behind them in the Constructors Championship, but it is of course early on in the season.
In terms of drivers though, it's not Mercedes who have a man at the top. Sebastian Vettel, who drives for Ferrari, is currently ahead of Hamilton.
The German is on 141 points, and behind him, the Brit is on 129. This is not something Mercedes are used to.
For all their success, both Hamilton and Rosberg were not always happy, especially with each other. The pair clashed a number of times, both on the track and off it, so it's obvious their relationship was just a working one.
Team Principal, Toto Wolff, has since revealed who of the pair was perhaps the one who would fight dirty.
When asked who the 'schemer' was, he told the Daily Mail:
"The one who is no longer here. The vicious one. Nico just tried to use all the weapons he had."
Wolff did go on to say though, that he has no hard feelings about the way Rosberg left the team, and that all his 'scheming' was down to a desire to win and be the best.
"There were all the psycho games that you can play to destabilise your rival."