Mercedes driver Valtteri Bottas saw his Formula 1 title aspirations take a severe blow after retiring from the Eifel Grand Prix.
The Finn arrived at the Nürburgring with momentum on his side after a win in Russia, increasing his confidence further by taking a superb pole.
Bottas then led throughout the opening stages of the race until suffering a lock-up on lap 13 before retiring with a loss of power six laps later, believed to be a problem with the MGU-H.
Declaring himself to be "unlucky", Bottas added: "What can I say? During the VSC I started to lose power and we never recovered.
"It was quite a big loss of power so it was something to do with the power unit. I have no details yet. It is unlucky but it was good fun until then."
At the start, Bottas initially ran wide at turn one with team-mate Hamilton fighting down the inside but fought back brilliantly to hold the lead.
But he later picked up a flat-spot with a mistake into turn one and was forced to relinquish his position with an early stop.
Bottas believes, though, he would have still had the pace to challenge had it not been for his retirement.
"It was a great start, we had a great battle and there was no way I was going to let it be easy for him," he added.
"I was glad that I could maintain the lead but obviously, later on, I had the lock-up into turn one and lost the position and it meant I stopped early. The new tyres were starting to feel good so I have no doubt that I had good pace."