AP Photo/Luca Bruno.

Bahrain - Lewis Hamilton on Monday admitted to concerns about Mercedes' early-season form after seeing Ferrari’s Sebastian Vettel remain unbeaten in Sunday's Bahrain Grand Prix.

The 33-year-old defending four-time world champion said he had little idea how or why Ferrari had been able to out-perform his Mercedes team, Vettel claiming a tense win ahead of Valtteri Bottas.

It was the German’s second win in as many races this season and installed him as a clear favourite to beat Hamilton to become a five-time champion.

"I am thinking and wondering," said Hamilton. "My thoughts are already on the world championship – I’ve lost two races in a row now and I am 17 points down after just two races.

"Obviously, the grid penalty was difficult to swallow here this weekend, but I think the team did a really good job.

"Hopefully, when we go to China for the next race, we will have a better understanding of the tyres and put up a better fight against Ferrari.

"Shanghai has been kind to me in the past so I am hoping I can bounce back."

Vettel won Sunday’s race despite admitting he felt Mercedes had him in 'check-mate' when they adopted a one stop strategy.

Mercedes boss Toto Wolff said he believed that move had given his team a "90 percent chance" of winning, with Bottas on durable medium tyres close behind Vettel who was on soft tyres and a two-stop strategy.

Strategy switch

But Ferrari switched strategy and asked Vettel to go the full distance – meaning he ran 39 laps on used soft tyres to complete the race.

"I think we had won the race already after coming out on the medium behind Sebastian, with a gap that we were able to close down, and knowing that they would either need to stop once again or they would run out of tyre," said Wolff.

"At that moment, I would say 90 per cent probability was on us winning - and we lost that."

Hamilton said he believed he lost the race in qualifying when he could not match Ferrari’s pace – as they locked out the front row of the grid and he had a changed gearbox that cost him five places.

"I could not make the moves I wanted to in the opening laps and that cost me," said Hamilton.

Wolff added that he was encouraged by the pace of Mercedes cars in the closing laps as they chased down Vettel without avail.

"What was interesting to see was that maybe the pace of the Ferrari was not as good as we expected," he added.

"They were fuel saving straight from the beginning which for sure cost them performance.

“Our pace was solid on the super-soft and actually I think we could have probably been able to go a little quicker."

Agence France-Presse