Williams pair 'evenly matched'

The pair will test again in the coming weeks before one of them is selected in time for the team's new chassis launch on 31 January.

"It is going to be fairly exhaustive," said Williams of the testing process. "Maybe after the first test it will be black and white and there is the light, but I don't think so. They are quite different drivers and very evenly matched in certain respects.

"I hope (we can get) some sort of certainty of which driver is quicker. At the end of the day if they are both the same I don't know what we will do... maybe toss a coin!"

Williams revealed that Pizzonia had been on the brink of securing a full-time race seat until BMW encouraged the team to consider Heidfeld as an alternative.

"We were on a course for Antonio, but Nick's name came up a few times in conversation and BMW said, 'look Frank and Patrick, this guy might be good, why don't you have a look at him?'" said Williams. "He is very quick. So that is why we will be testing him again."

He denied that BMW would prefer the team to choose Heidfeld because of his German nationality.

"No. I always thought that what is important to them (BMW) is results and good press, especially in Germany," said Williams.

The team has had to find replacements not just for former race drivers Juan Pablo Montoya and Ralf Schumacher - who left for McLaren and Toyota respectively - but also for its former test driver Marc Gene, who has departed for Ferrari after four seasons as Williams' primary reserve driver. Williams hopes that, whatever the outcome of the forthcoming tests, both Pizzonia and Heidfeld will remain with the team so that whichever is not chosen for the race seat can take Gene's place.

"Whoever loses will still be offered a test drive," he confirmed.