SOCHI, Russia - After four evenly-contested races, Formula One returns to its European homeland with Ferrari revived and a fiercely-competitive season ahead as champion Mercedes battles to retain its crown.

That much became clear after last weekend's see-saw battle at the Sochi Autodrom, where popular Valtteri Bottas of Finland secured his first victory for Mercedes while puzzled teammate Lewis Hamilton struggled to finish fourth.

The Mercedes duo was separated by the two Ferraris of championship leader Sebastian Vettel and Kimi Raikkonen in a race that saw little overtaking, but much tension.

"The season is going to be extremely close," said Mercedes team boss Toto Wolff.

"More than very close. Ferrari has a good car. They have come back from the winter with a very good car and it seems to suit Sebastian very well - so we just need to stretch ourselves to perform as good as we can."

Bottas' win rescued Mercedes after Ferrari dominated qualifying, with four-time champion Vettel taking the pole and Raikkonen alongside him - the team's first front row lockout in nine years.

The unflappable Bottas has proved already he is not only very different to retired 2016 champion Nico Rosberg, but likely to be just as formidable a teammate to three-time champion Hamilton.

"For me, it is just the start, the beginning of the year," he said. "It's too early to talk about the championship in any detail.

"We are just focusing on making the car better and that will give us more wins for both cars.

"Getting the first win is something special, for sure, even though you always believe in yourself.

"If you think you are not able to win you should stay home, but to get confirmation and get a good result, that matters in this world.

"How many races you can win and get on the podium is the name of the game. Getting my first win gives me a lot of confidence - even though I always knew I had the ability. It is not that simple this year. It's going to be a massive fight."

After reigning supreme for three years, Mercedes faces a scrap.

Last year, it won 19 of the 21 races, failing only twice and already, in four outings this year, it is two apiece with Ferrari.

As a result, although Mercedes holds a one-point lead in the constructors' championship, Vettel leads Hamilton by 13 in the drivers' title race as the teams prepare for the introduction of major upgrade packages at the Spanish Grand Prix on May 14.

Bottas' win might make life awkward for Mercedes and Hamilton if Ferrari shows favor for Vettel, who has 86 points. Hamilton is second with 73 while Bottas has 63 and Raikkonen sits fourth with 49.

Wolff explained last week he prefers to see Mercedes drivers racing each other, without team orders, because it pushed the team development and overall pace, but such a scenario is less likely at Ferrari.

Vettel expects a close contest between the major teams, but believes also that Red Bull will force its way into the picture when it introduces its updated car at Barcelona.

"There are so many rumors going around now and I know they can build a quick car so, for me, it is a question of when, rather than if. It is going to be exciting," said the German.

The emergence of Bottas adds to the mix for the championship in many ways. His relationship with compatriot Raikkonen is not close and has often created intense on-track rivalry.

He is also showing, with his pole position in Bahrain and victory in Sochi, that he has the pace to beat teammate Hamilton.

For now, however, he said he is content to take it one race at a time and enjoy his successes.

"I have to say that I am not normally that emotional, but when I heard the Finnish national anthem it was something quite special for me. It felt very good!"

Agence France-Presse