Sebastian Vettel believes his biggest worry this weekend is not his rivals, rather it's the threat of rain falling during the grand prix.
Red Bull have yet to claim a victory this season when it has been raining, losing both the Australian and Chinese Grands Prix to McLaren's Jenson Button.
In fact, Red Bull's only win, which was secured by Vettel, came in Malaysia, which was a race weekend that saw the rain cause havoc in qualifying but fail to materialise during the grand prix.
This weekend's Spanish GP could once again see rain hamper proceedings with a slight chance of showers during qualifying and Sunday's race.
And that is the one thing Vettel, who was quickest in Friday's practice ahead of his team-mate Mark Webber, does not want to see.
"The weather!" he told Autosport when asked what his biggest worry was for this weekend's grand prix.
"I think it was quite chaotic especially the last race, so we try to execute a clean Sunday and a clean race. It doesn't help when it starts to rain and stops raining every five minutes.
"Even then you have to do a good job, and last time we didn't succeed the way we wanted to. But here we will see what we can do."
Aside from the weather, though, there could be a few other concerns for Vettel as his rivals, like Red Bull, enter this weekend's race with major updates to their cars.
But whether that will negate Red Bull's qualifying supremacy remains to be seen, although the German is expecting a closely fought battle.
"McLaren, Ferrari and Mercedes, all three teams look very strong," he said. "It has been very close. In some races we were stronger than others, but in other races it was much closer, then sometimes McLaren was strongest and fastest.
"So it is tough, it is tight. We will make a step here, but it depends how big your step is compared to the others. If you find half a second then great, but if others find one second then it is rubbish."