BARCELONA, Spain - Jenson Button admits he's baffled by McLaren's struggle for pace in Bahrain after such a strong season start and is hoping for better from this weekend's 2012 Spanish F1 GP.Button won the opening race in Australia and his team mate Lewis Hamilton took pole position for the opening three races. Despite this, it was rival teams Red Bull and Lotus that dominated proceedings in Bahrain while Button retired from the race and Hamilton had to settle for eighth.NOT A PERFECT WEEKENDButton was struggling to understand the unfortunate change in pace: I think we have a very good car, we proved that in the first race and in Shanghai we were very quick but I wouldn't say it is the quickest car."If you look at the last race, it wasn't the perfect weekend for us but we basically weren't fast. The Lotus and the Red Bulls were a second quicker than us so I don't understand why and no one else in F1 understands knows why it is such a change around but I don't think they have a car that is a second quicker than us," he said.Button suggested that different track styles and conditions could be a key factor but admitted he could not tell who is favourite to win in Spain.Button said: "I think it is circuit dependent and I also think that the conditions make quite a big difference, I know we always talk about tyres but the conditions make quite a big difference as to whether you can get the tyres working on a particular car.'CAR DOESN'T STAND OUT'"It is very difficult to understand at the moment who is quick. You would say at Melbourne and China it was us and Mercedes and at the last race it was Lotus and Red Bull. I have never been in a situation where there are so many teams fighting for victories at different circuits," he said."So I wouldn't say that our car stands out compared to the competitors and we say that you are only as good as your last race and you would say now that the Lotus and the Red Bull are the cars to beat," said Button.Stay with Wheels24 for the 2012 Spanish Formula 1 weekend.