As he casts his eye over the driver market in search of a replacement for Red Bull bound Sebastian Vettel, team co-owner Gerhard Berger has sent out a clear message to four-time Champ Car champion, Sebastien Bourdais.

Quite simply, the Frenchman has been out-raced, out-qualified and out-classed by his German teammate, and now has to seriously look at whether he will be able to retain his seat in 2009.

While Bourdais has scored two points, having finished seventh on his promising F1 debut in Melbourne, his highly-talented teammate has scored nine, including a highly-impressive fifth in Monaco.

Speaking to Formula1.com, Berger has warned Bourdais that he must raise his game in the remaining six races.

"In Formula One you have to give someone half a year before you start to judge him," said the Austrian, who in a fourteen season F1 career won ten Grands Prix, finish third in the World Championship on three occasions.

"The half year is over and he (Bourdais) is now in a situation where he has to prove his talents," he continued. "I would not say I already have a clear opinion on him but I also have to say Sebastian Vettel started a couple of races before and he performed very well in the first half year."

Asked if Bourdais will retain his seat for next season, Berger, who won races for Benetton, McLaren and Ferrari, replied; "No, it's open".

Looking ahead to 2009, which sees Bruno Senna and Sebastian Buemi linked with the Faenza-based outfit, Berger said: "Everyone will bring opinions and then we, Dietrich Mateschitz and myself, will try to find the right way for the team.

"At the end of the day the last word will come from Red Bull," he admitted, "because that is where we get all our resources from. So it is natural we listen to what he would like to do."

In fact, Red Bull, like Toro Rosso, is in urgent need of outside sponsorship - as opposed to contra-deals - and financing, which therefore makes one of the suggestions we have heard seem quite plausible.

As Takuma Sato's manager Andrew Gilbert-Scott seeks a test for the Japanese driver with Toro Rosso, we hear that it is not entirely impossible that in addition to sponsorship, the former Super Aguri driver might be able further sweeten a possible deal with a supply of Honda powerplants.

Following the collapse of Super Aguri, the finger of blame was roundly pointed at Honda, and it remains to be seen how the Japanese team is treated when it arrives at the Fuji Speedway. Imagine therefore, how Honda might be treated were it to announce ahead of the race that it has not only done an engine deal with Toro Rosso but also found a berth for the highly-popular Sato.