Representatives from both Renault and Mercedes believe Formula 1's midfield could threaten the dominance of the top three teams based on testing so far.

So far, over the six days of running in Spain, no team has particularly emerged as clear favourites, with the pace Ferrari showed last week matched by Red Bull and other teams not far behind.

In fact, McLaren's Carlos Sainz set a new fastest time on Wednesday, a 1m17.1s on the C4 tyre, which matches the best hypothetical time seen when tyre-corrected, a 1m16.5s.

“I see everybody [as a potential rival]," Mercedes motorsport boss Toto Wolff claimed.

“There could be Red Bull for sure. It has the resource to be competitive, and it has always been a flexible team to adapt to new regulations, and even change directions.

“Ferrari has just got stronger and stronger and stronger.

“Then Renault was the quickest team on the last few days [last week], Toro Rosso was unbelievable, Alfa Romeo was very good.

“So all of them; there could be a situation where we are all very close together and there could be surprises.”

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New Renault driver Daniel Ricciardo echoed the Austrian, insisting the French manufacturer isn't guaranteed to start the new season as the fourth best team.

“I would like to think that we are at the front of it, but there is no hard evidence that we are," he told Motorsport.com.

“Our objective first and foremost is to be fourth or better in the teams' standings, but it is really trying to hone in on the gap to the top three.

“As you know, it is big so it is not going to happen overnight, but absolutely the target this year is to close it in, close it in, and try to develop the car."

While initially sounding sure that there would be a similar two-tier grid to last year, with more thought Ricciardo was then less convinced.

“It definitely looks like it is close in that midfield group. I would assume now that the top three teams still have a bit of a margin on the others, but I don’t know," he said.

“If you look at Sainz’s time, and even if it is on the softest tyre, it is still a 17.1s. So it is fast, but again because we are not all out at the same time with the same fuel loads, if someone does a time at 10am then by 11am it can be completely different.

“Realistically we are not going to know until qualifying in Melbourne when everyone has the same fuel, same tyres, same track conditions.

“But I would at the moment say that that midfield group looks close. Everyone is able to do a low 1m17s, which is good for you guys I guess. I want to get away from that.”