Mercedes motorsport boss Toto Wolff said he would re-break his arm if it offered a guarantee neither of his team's cars would endure any more reliability issues this season.

Following Nico Rosberg's early retirement in Sunday's Singapore Grand Prix, there is deep concern inside Mercedes the destiny of the title will be determined more by luck than by skill out on the track.

Mercedes have scored seven one-two finishes this year and are poised to wrap up the constructors' crown in one of the next two races in Japan or Russia. But there have now been four mechanical retirements – two apiece for Lewis Hamilton and Rosberg – plus issues for the former in both Germany and Hungary in qualifying that cost him points.

With Hamilton now in possession of the championship lead for only the second time this season, and first time in four months, just three points separate him from Rosberg.

It is almost a level-playing field, effectively making the rest of the season a five-race title fight, but with both drivers knowing another reliability hit could prove fatal to their title hopes.

Wolff, who broke his right arm and collarbone in a cycling accident two months ago, said: "We have a great team dedicated to quality, and I'm really proud of that department.

"Despite that, it's even more astonishing we continue to have these issues.

"I guess it takes time for the whole group to come together and time until we stop suffering from these DNFs (did not finish) which are unacceptable for us as we have had four of them now.

"If we could do anything more to stop the DNFs then we would do it. I would break my arm again! "We just have to get on top of the problems."

Asked as to whether he was worried unreliability would prove to be the decisive factor, Wolff replied: "That is something that would not be satisfying at all.

"We don't want any spin in there that the championship was decided because one car let down the driver.

"We need to re-focus, get our heads down and keep concentrating on what we can do, what the utmost is, to prevent reliability problems for Nico and Lewis."