Nico Rosberg was "at his best" during the Bahrain Grand Prix, according to Mercedes boss Toto Wolff.

Rosberg was overtaken at Turn 1 by Kimi Raikkonen, dropping him to fourth, but soon passed the Finn and his Ferrari team-mate Sebastian Vettel with some ballsy late braking moves down the inside of Turn 1. A brake-by-wire failure on the penultimate lap meant Rosberg was unable to defend second from the charging Kimi Raikkonen and had to settle for third.

Having lost the 2014 title to Mercedes team-mate Lewis Hamilton, Rosberg has not beaten the world champion in qualifying or a grand prix so far this season. His form has come under scrutiny as a result but Wolff says the German showed his class in Sakhir.

"First of all you must be happy with one and three, no doubt about it," Wolff said. "But losing second place with Nico ... Everybody who ever doubted in Nico saw Nico at his best, fighting hard, overtaking. Losing that position because of a brake failure is a pity. All in all one and three one and three has to be satisfactory and that is Formula One at its best, I would say."

Wolff said Rosberg's aggressive driving in the early stages of the race did not lead to the failure.

"We saw very hot brakes on Nico's car in traffic following Kimi and Sebastian, then lots of fighting, lots of hard-braking. So we monitored that, but in the end with the backmarkers and lapping cars those temperatures went through the roof and we had brake-by-wire failure on both cars at the same corner. Leading into the last lap it was on the hard braking on the straight that temperatures went sky high and when that happens the brake-by-wire system switches into the conventional system, then you are without weapons to defend."

Asked what Rosberg needs to do to swing momentum back in his favour, Wolff pointed at the example being set by Hamilton in the other Mercedes.

"Qualify on pole and control the race from there. You could see Lewis qualifying from pole and running away and being in control of the race, similar to what we had in China, is the key to maximum points. It's four races into the season, there's another 15 left ... quite a lot. So I have no doubts after his driving [in Bahrain], which was exceptional, we'll have a strong Nico bouncing back in Barcelona."