Sebastian Vettel's last season with Red Bull failed to improve Saturday, with the four-time defending F1 champion enduring another poor qualifying session at the inaugural Russian Grand Prix.

Vettel failed to make it into the final of the three qualifying sessions but will start 10th because of another driver's penalty.

The German has announced that he is leaving Red Bull at the end of the season. He has not said which team he will join, but all speculation has pointed to Ferrari.

Vettel says he "wasn't comfortable in the car today. It was very difficult."

Teammate Daniel Ricciardo, who has had a more successful season, will start sixth, also benefiting from the five-place penalty for Kevin Magnussen of McLaren.

Red Bull is set to lose the constructors' title to Mercedes.