By Jonathan Noble Thursday, October 23rd 2014, 09:29 GMT

Red Bull boss Christian Horner says Mercedes' Formula 1 title success this year has served to fire up his team to do better in 2015, rather than leaving it depressed.

After winning the last four consecutive world championships, Red Bull's rule over F1 officially came to an end when rival Mercedes clinched the 2014 constructors' crown at the Russian Grand Prix.

Horner said the writing had been on the wall for Red Bull ever since its disastrous pre-season testing form, but he felt that his outfit could take encouragement for having kept the battle open so long.

"We've had a little bit of time to get our heads around it - from February in reality," he said.

"So, in all honesty Mercedes have done the best job this year and all it does is motivate you.

"You know how much work goes into winning a championship and we did it four times in a row, which is an enormous achievement. And while we had a disastrous year, we are still second."

He believes Red Bull has now proved itself in adversity, and believes engine partner Renault's winter developments will allow it to close the gap again.

"We are the only other team to have won a grand prix [in 2014], and three of them at that," said Horner.

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F1: Red Bull: Mercedes isn't depressing