Renault have pledged their support for Nelson Piquet after another difficult day for the Brazilian rookie at the Canadian Grand Prix on Friday.

Piquet, son of the triple Formula One world champion and namesake, has finished just two of his six races so far this season and has yet to score a point.

The 22-year-old was 11th in Malaysia and 15th in Turkey.

The Brazilian suffered a gearbox failure in Sunday's second free practice session and ended the afternoon last and more than two seconds off the pace.

But Renault engineering head Pat Symonds and Piquet's team-mate Spaniard Fernando Alonso both said they were confident in Piquet's ability.

"I think we need to support him," Symonds told reporters after practice.

"It is very easy to be critical of drivers in a situation like that and I think people have very short memories in motor racing."

"Of course you can look back exactly a year, to this very event, to the problems (former Renault driver) Heikki Kovalainen was having," he added.

"He was having a dreadful season and really finding it difficult. I think on the Saturday in Montreal last year it was very hard to imagine a driver having a worse day. He had two big accidents, one in qualifying and he finished fourth in the race and he never looked back from that Sunday onwards.

"So much is in a driver's psyche that once they break through there is no stopping them," said Symonds. "What we have got to do with Nelson is help him break through that barrier. Just one good result and it will come on from there."

Piquet's father retired in 1991 rafter winning 23 grands prix. His last victory was in Canada for Benetton, the team later bought by Renault.