Former Ferrari Formula 1 team principal Stefano Domenicali believes Fernando Alonso's appearances at the Indy 500 and now a WEC program is about proving he is "one of the best in the world".

Domenicali, who now works for another Italian brand, Lamborghini, was at the helm at the Scuderia for both of the Spaniard's near-title misses in 2010 and 2012 and ultimately oversaw what was considered a potential dream pairing of Alonso and Ferrari end in disappointment.

The double world champion would move on to McLaren in 2015, another chapter that has not had a happy ending and it is for that reason his former boss claims he has looked elsewhere.  

"Fernando is looking for challenges outside of F1 because his team is going through a difficult period," Domenicali told Italy's Corriere dello Sport. "He wants to demonstrate his skills, to prove that he remains one of the best in the world.

"Today at the top there are three drivers: Alonso, Hamilton and Vettel. The differences between them are minimal and depends on the cars they drive."

As the motorsport world continued to react to the news on Tuesday that the 36-year-old would be racing with Toyota in the WEC, the man himself was already behind the wheel of his LMP1 machine, taking part in a test day at Motorland Aragon in Spain.

This marked his second appearance with the Japanese manufacturer, after driving with them in Bahrain in December, and two more private tests are planned before the Prologue event at Paul Ricard in April.