McLaren boss Martin Whitmarsh has ruled out talk of the world championship being a two-horse race between his team and Red Bull, while also confirming that there is no number 1 at the Woking outfit.

In the latest Vodafone McLaren Mercedes phone-in press conference, Whitmarsh was asked whether he sees the title fight as a two-horse race, with Ferrari falling by the wayside, and with nine rounds remaining he clearly doesn't.

"I'd love to believe that, but experience has told me that you can't write them off," he replied. "Ferrari are a strong team, they're technically capable, have fantastic resources and they have one former world champion and one other top-flight driver.

"Mercedes, similarly, have one former multiple world champion and a very good driver in Nico," he continued. "So I think it's too early to write them off. We need to improve our car and do as good a job as we can do. Red Bull clearly are the principle challenge at the moment, but I don't dismiss the others."

With an eye on the situation at Red Bull, Whitmarsh was asked if his team will soon need to make a decision in terms of which driver to favour over the other.

"Not yet," he replied. "Jenson is second in the Drivers' Championship, has had two great wins this year and has proven that he's a great driver, a great reader of the race and also someone who could recover from 14th to fourth is a phenomenally quick and adept racing driver, and also has a lot of determination.

"I'm sure Jenson hasn't given way to Lewis's charge for the championship. He will want to win this weekend, he will want to move that momentum back in his favour, and that's just how it should be."

At Valencia and again in Britain, Hamilton made contact with Sebastian Vettel at the start, Whitmarsh was asked if he was concerned that the 2008 champ's uncompromising nature could work against him.

"You want them to be as aggressive as they can be," he replied, "provided the car comes round intact and not requiring a pitstop at the end of the first lap.

"A Formula 1 standing start is one of the most exciting spectacles," he continued, "and it's a very critical phase of the race. You have to take some risks. You have to have a degree of aggression to do it well. I believe Lewis has done very well, so indeed has Jenson, he came round from 14th to eighth in one lap at Silverstone, which I believe was mighty impressive. You don't overtake cars like that without taking some risks, and the skill of the really great drivers is balancing that risk and taking the requisite amount of risk for the gain that is possible at the start. I think both drivers have done a very good job in that regard."

Having removed its blown diffuser after the two Friday practice sessions at Silverstone, the team intends doing back to back tests with it in Germany. Whitmarsh was asked to explain how the process will work.

"One of the challenges is that whereas flaps, wings and various aerodynamic appendages are fairly quickly changed on the car, so, during the course of a session, you can do back to backs and, for example, drivers can change front wings mid-run, the blown diffuser is a completely different floor, different heat management components and obviously different exhaust. Therefore it's not possible to perform an in-session back to back and it's even quite difficult between sessions so I think you've just got to rely on the data that we've previously collected.

"There may be components as part of the blown diffuser that we change between the cars, so there is a compromise. In the old days we'd go testing, you'd prepare two cars and run them alongside each other. We can't do that. We're torn between the priorities of developing the car and looking at longer-term improvements, versus the very limited amount of track time that the drivers get in order to understand that particular event and that race circuit, as they haven't been to Hockenheim for two years, and make sure that they're as prepared as they can be for Saturday qualifying, which is critical."

Asked if the team might run one car with the blown diffuser in the race and the other without, he replied: "We're working at the moment on the premise that we'll have blown diffusers on both cars to start with. At Silverstone Lewis wanted to keep the blown diffuser on on Friday night, but we took the decision there to switch them both back to the older diffuser.

If there is a preference from one side of the garage to the other, and if I can, we'll avoid that, we'll do it if we think it's the right way to perform during the course of that weekend. There are advantages, as you can imagine, to running one car in one configuration and one in the other, provided that in so doing, you don't end up, rightly or wrongly, accused of treating the two drivers differently."

Referring to the difference between the tyres on offer this weekend - hard and supersoft - he said: "I think it's the broadest spread of tyres that we've seen so far, and therefore it's likely to have an impact on some of the strategy and how the race runs.

"The super-soft is likely to be quite a short, light tyre, so if you qualify on the super-soft and others behind you are able to fit the prime then that's going to have some impact on how you run the race."