Wehrlein drafted in by Mercedes for Wednesday

Manor's Pascal Wehrlein has been called upon by Mercedes to assume testing duties today at the Circuit de Barcelona-Catalunya.

The German and Mercedes protégé was switched with Renault driver Esteban Ocon, who was scheduled to run today for Mercedes, because the Brackley outfit wants to rely on a driver with race experience to conduct its specific testing program.

The decision will obviously leave Ocon frustrated, as the French driver was looking forward to his Wednesday stint following a productive run with Renault yesterday.

While Ocon is contracted to Renault and will be handed a few free practice outings by the French manufacturer this year, having replaced Jolyon Palmer last Friday morning in Spain, the former GP3 champion still remains in the Mercedes stable.

Interestingly, Ocon commented yesterday on Renault's new upgraded power unit, claiming the new B-spec engine was "really, really good".

So perhaps Mercedes took note of the Frenchman's assessment and are now reluctant to provide him with track time and access to information he could potentially share with Renault for the benefit of its power unit, which also powers Red Bull.

Mercedes decision to run Wehrlein also means that Lewis Hamilton will not be taking part in the Silverstone test later this year, with Mercedes having to run a driver who has started no more than two races in his F1 career on both days. Hamilton also did not take part in any in-season tests last season.

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Phillip van Osten

Motor racing was a backdrop from the outset in Phillip van Osten's life. Born in Southern California, Phillip grew up with the sights and sounds of fast cars thanks to his father, Dick van Osten, an editor and writer for Auto Speed and Sport and Motor Trend. Phillip's passion for racing grew even more when his family moved to Europe and he became acquainted with the extraordinary world of Grand Prix racing. He was an early contributor to the monthly French F1i Magazine, often providing a historic or business perspective on Formula 1's affairs. In 2012, he co-authored along with fellow journalist Pierre Van Vliet the English-language adaptation of a limited edition book devoted to the great Belgian driver Jacky Ickx. He also authored "The American Legacy in Formula 1", a book which recounts the trials and tribulations of American drivers in Grand Prix racing. Phillip is also a commentator for Belgian broadcaster Be.TV for the US Indycar series.