Ralf Schumacher decided move on from Williams because he no longer believes he will be able to win the championship with the team. Schumacher, who is now signed to Toyota, was unhappy with the FW26 this season and doesn't think Williams will be able to challenge for the title next year.
"It was the worst season I have ever had in a Formula One car," he said of 2004, according to the UK's Sunday Mirror. "Of course there was the accident but just as frustrating was the fact that we were not as competitive as we wanted to be on the track."
"If I had been in a car capable of challenging for the title this year and felt we could win it next, then I would have stayed at BMW Williams. But that was not the case. My target is to win the World Drivers' Championship. I want to be the best. Sadly, it has not happened."
"Each time both myself and the team were left a little frustrated at the end. I decided it was time to go somewhere else. When you stop believing it will work it is time to move on. In any sport you can sometimes stay in the same place too long. This was the right thing to do."
Toyota has yet to really prove itself in F1 but Schumacher expects that to change, and that the team will be able to give him a car with which can fight for the title. The German didn't think any other team could have offered him a better opportunity.
"Toyota are a young team who have only been involved in F1 for a couple of years," he said. "They are ambitious, like myself, and believe they can put together a car able to compete for both the Drivers' and Constructors' Championships."
"Where else could I have gone? Apart from Ferrari, it's difficult to see which other team could give me what I want. Toyota have a five-year plan to get to the very top in F1. It may be a risk but it's an exciting one."
Schumacher will be teammate to Jarno Trulli at Toyota in 2005. His former Williams teammate, Juan Pablo Montoya, is also moving on, to McLaren. Williams has Mark Webber for next season and is speculated to be making a decision about its vacant race seat after the initial bout of winter testing.
Mika Hakkinen is now out of the equation, as he has signed to drive for Mercedes in the DTM next year. It's rumoured that Nick Heidfeld, David Coulthard and BAR third driver Anthony Davidson are likely candidates to test for Williams in Spain, along with the team's test driver Antonio Pizzonia.