Singapore GP to throw up 'curveballs' predicts Daniel Ricciardo

The time gap between the soft and the super-soft Pirellis was around 2.5 seconds and, with early indications pointing towards a three-stop race, strategy variations could mix things up on Sunday.

Ricciardo said: "To be quick on the tyre is one thing, but to make it last five more laps is another - and that can save you doing an extra pitstop in the race.

"It is going to be a real tyre fight in a way this weekend, perhaps the race will throw a few curveballs."

Pirelli motorsport director Paul Hembery admitted the gap between the tyre compounds was larger than expected, which complicates things for Sunday.

"It is bigger than we thought," he told AUTOSPORT. "We expected just about two seconds and it was averaging out at the end at 2.5 seconds.

"Thermal degradation was pretty much what we expected in Singapore, and that pushes us towards a three-stop race as they will have to use the super-softs from qualifying.

"I think we have a 100 per cent record of safety cars here as well, so that could make some of the strategy interesting."

RED BULL EYES MERCEDES CHALLENGE

Although Red Bull ended the day three tenths of a second down on Mercedes, its drivers felt there was still the chance of challenging championship-leading team.

Ricciardo reckoned that Mercedes has more pace up its sleeve, but insisted Red Bull had room for improvement too.

"Looking at it, it looks good," said the Australian. "But I feel they have a bit more in the tank.

"I think if they got the best out of their car here this weekend it would be half a second in front. But if it is in truth three tenths, then that is a reachable gap."

Vettel, who felt he had more laptime in him after limited running in the afternoon due to engine problems, was also optimistic.

"I was not able to get the best out of the tyres straight away , but overall I am pretty happy and I am sure we can improve the car. We should be in a good place tomorrow," he said.

"We are a lot closer to Mercedes than we have been. Qualifying is tight but we will see what we can do."

Mercedes appeared unconcerned by the margin over its rivals though - with Nico Rosberg saying there was no reason to feel its run of poles was under threat.

"We've seen now in the last couple of races that on Friday they're a bit closer, so I'm hoping it will be the case that as the weekend goes on we just edge away a little bit," he said.