Sebastian Vettel claimed there was work to be done by Ferrari to keep up with Mercedes and Lewis Hamilton, with the championship leader not too happy after both Friday sessions were completed.

Although the German saw teammate Kimi Raikkonen finish on top in the morning and keep his Ferrari in second place splitting the two Mercedes' in the afternoon, his own pace was quite disappointing in third and fifth overall.

Before the weekend, Mercedes was expected to have the upper hand over the Scuderia and looking at the relative performance of the two teams, Vettel acknowledged a tough fight awaits.

“I think they looked very strong,” he said. “Whenever they went out, they had the possibility to go fast. It's a long track and it's not so easy to put everything together, so I guess what everyone is looking at always the times, the lap time itself, but there's a bit more to it.”

“I think for us, for myself, I was not happy. I was a bit so-so. I did not really find the rhythm, especially on the short run.”

However, the German admitted his car felt good on the long runs and that some work can be done to get it in perfect competitive shape.

“The long run was better. Overall I think the car is there to do the job to go fast. We just need to get it right on all fronts. I need to do my job and we'll be fine.”

Considering where Ferrari can improve, Vettel will be looking to understand the behaviour of the tyres even more, with that being a huge factor in affecting race results this season and particularly this weekend.

“We're missing some answers on the tyres but overall I think the car is OK," he said. "We saved some mileage which is good with the rain, but obviously it was not the target. We just need to put it a bit more together.”

One thing Vettel certainly seems to have enjoyed so far is the thrill of driving the 2017 cars around the spectacular Spa layout.

“It's a nice track, obviously with these cars there is more grip and it's more fun,” he said. “Eau Rouge and Blanchimont are pretty straightforward, easy flat, but the middle part got more exciting. It should be nice tomorrow.

“I don't know what's the weather forecast. I guess it should be dry tomorrow, but we'll see anyway. If we get it right, it's always fun.”