“We leave Valencia knowing we've got a quick car ”
Christian HornerRed Bull boss
"It's bad, but you can't change it now," said the world champion.
"Up to that point we were very strong. I felt happy, we were very quick."
The Red Bull featured a major aerodynamic upgrade at the rear of the car for the Valencia race and it led to the most dominant performance shown by any car so far this season.
Vettel was on pole by 0.324 seconds, while the next six cars were separated by a similar gap.
He then streaked away at the start, leading by four seconds after two laps, and was 20 seconds in front when the safety car was deployed on lap 30.
The alternator failed on his Red Bull on the lap the race was restarted, and Lotus's Romain Grosjean - whose car uses the same Renault engine as the Red Bull - suffered the same failure while running second a few laps later.
The race was won by Vettel's title rival Fernando Alonso, who is now 26 points - more than a race win - ahead of Vettel after eight of the 20 races.
Vettel stumped by Valencia exit
Vettel has also fallen behind his team-mate Mark Webber, who recovered from 19th on the grid to finish fourth.
McLaren's Lewis Hamilton slipped from the head of the standings to third following his failure to finish after a collision with Williams driver Pastor Maldonado.
Red Bull team boss Christian Horner said: "I think he [Vettel] took solace in his performance.
"It's a long championship, Fernando has done a tremendous job, he has scored in every single race but statistics say he has to have one bad weekend in 20, so it will hopefully balance itself out over a season.
"We leave Valencia knowing we've got a quick car and Mark very much demonstrated that in his recovery from 19th on the grid to fourth on the road.
"We see form fluctuate from circuit to circuit but we've had three poles in the last three races.
"We were in a commanding position here, tyre degradation we were able to match our nearest rivals, so on that side it's been positive.
"Obviously it's very disappointing to have a DNF [did not finish], the first mechanical retirement we've had since Korea 2010, but I'm sure together with Renault we'll learn from it."
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