Sebastian Vettel's pole position for the Russian GP could prove to be a critical turning point in the 2017 Formula 1 title race, according to Sky F1's Martin Brundle.

The Ferrari driver inflicted Mercedes' first Saturday defeat in 19 events as he topped Ferrari's first front-row lockout in almost a decade in a dramatic reversal of fortunes in Sochi.

"When you look back over the championship season, often there are some turning points and key moments, and if Vettel wins the title, that lap of his today may be one of those key moments," said Brundle.

"He just aced it over his team-mate, got it on the front row, and gave himself the chance to drive off into the distance."

Ferrari appeared to hold a significant advantage over Mercedes on race pace in Friday practice and, critically, able to preserve tyre life far more effectively than their title rivals.

Vettel on pole position as Ferrari topple Mercedes

Adding to Vettel's advantage, he will start Sunday's race three places ahead of Lewis Hamilton, his nearest championship rival, after a trouble-filled afternoon for the Mercedes driver.

"Hamilton was half a second adrift - he really had an awful qualifying by his standards," said Brundle during Sky F1's coverage of Saturday's thrilling qualifying hour.

"Everytime we've gone on board with Lewis he's been having a drama, the car will just not stick to the road."

Round four of the 2017 season begins at 1pm on Sky Sports F1.

Will Ferrari stay ahead of the pack in Sochi? Watch the Russian GP weekend with Sky Sports F1. The race begins at 1pm on Sunday. Check out all the ways to watch live F1 on Sky Sports for subscribers and non-subscribers - including a NOW TV day pass for £6.99!