SPA - Valtteri Bottas believes his much-improved Mercedes-powered Williams team have their best opportunity of the season at this weekend’s Belgian Grand Prix.

As Formula One returns from its annual August holiday, four weeks after the Hungarian Grand Prix where Daniel Ricciardo claimed a surprise victory for Red Bull, the two Mercedes drivers Nico Rosberg and Lewis Hamilton will continue their almost private duel for the title. But the intensity of the battle to catch and, at some circuits, challenge them for victory will increase as the tension rises in the closing eight races of the 19-round season starting at the majestic old Belgian track in the forests of the Ardennes.

“I think in theory Spa, and Monza, should be the next really good ones for us, maybe the best opportunities of the season,” said Finnish driver Bottas. “But we need to aim to be strong in other places and we can’t just rely on our good top speed.” Bottas believes that the power advantage provided by the Mercedes engines, and an efficient aerodynamic package, will enable the Williams cars to be extremely competitive in Belgium and Italy and a threat to both the Mercedes factory team and Red Bull, whose Renault engines this year have been disappointing.

Bottas’ view is supported by that of Williams performance boss Rob Smedley who said: “Both tracks will suit our car very well — mainly due to the fact the power sensitivity at those tracks is very high. Every horsepower you have is worth more there than at other tracks.

“We know our car is very strong in these areas. Additionally, I think at somewhere like Spa, with harder compounds, it can sometimes be quite difficult to get the tyres turned on and I think our car can do that.”

If all that spells problems for the Mercedes men, they are unlikely to show it and are sure to give the fans a strong showing whatever the weather at Spa-Francorchamps, where a capricious micro-climate can often produce rain and sunshine simultaneously at different places. Felipe Massa, who has started to show strong form at Williams, also believes a victory is possible. “I think it won’t be easy, but it’s not impossible,” he said. “Maybe at a few of these tracks we can have more chance.”

As the drivers and their teams return to action, they will be joined by a new face in three-time Le Mans 24 Hours winner Andre Lotterer, who has replaced Japanese Kamui Kobayashi in the Caterham team. The German, 32, has emerged as a single-seater racer this year in Japan’s Super Formula series after being a leading member of the Audi factory team in the world endurance sportscar championship.

“I’m ready for this challenge and I cannot wait to jump in the car and make the most out of the weekend,” said Lotterer. “I will need to get settled and used to the car quickly.” As Lotterer arrives with intent, Red Bull have lamented their likely lack of competitive performance in the next two races with team chief Christian Horner admitting they will struggle unless it rains. “It will be damage limitation in the next two races for us,” said Horner.

“Force India will suddenly reappear, Williams will be quick, McLaren will be quick and obviously Mercedes will be quick. “We have to take what we can out of the next two races, and then for the ‘fly-aways’ really try to turn things up.”