The Spaniard has been racing his double world champion compatriot since 2001 -- first in Formula One and then for fun in go-karts -- and says Alonso's will to win is as fierce as ever.
"What really impresses me about Fernando is the fact that he’s 41 and he’s exactly the same Fernando with the same hunger as I met in 2007," De la Rosa, who now has an ambassadorial role at Aston Martin, told Reuters ahead of Sunday's Saudi Arabian Grand Prix.
"There’s no difference whatsoever in his approach, how hard he’s working and how hard he’s trying and pushing everyone.
"Physically he’s young, he’s been taking care of himself and he’s pushing incredibly hard in every little detail -- not only on the car, on the team, but also physically on his training regime, on his diet. He’s a very complete athlete."
De la Rosa was test driver at McLaren in 2007, when Alonso joined from Renault as champion and Lewis Hamilton came on board as a rookie, and they worked together at Ferrari after that.
Back in 2001 the now 52-year-old was with Jaguar when Alonso debuted at Minardi.
De la Rosa said, in an interview organised by the team's non-alcoholic beer partner Peroni Nastro Azzurro 0.0%, that even in uncompetitive cars Alonso had kept pushing as if chasing the title.
"It’s the fact that he hasn’t thrown in the towel at all ... he didn’t need to see the carrot of the podium to be 100%," he said.
"He was always giving 100% even if he was fighting as a double world champion for 15th position."
RECORD-EXTENDING START
Alonso, champion in 2005 and 2006, will be making a record-extending 357th start this weekend with a team now second in the championship after finishing 2022 in seventh place.
No driver has ever won after 300 starts but Alonso, again third in first practice behind the Red Bulls in Jeddah, could become the first.
"If it’s not this year, it will be next year," said De la Rosa of a possible 33rd win.
"The expectation that Fernando’s podium in Bahrain has given the team, Formula One in general ... it’s beautiful to watch."
De la Rosa could fill a book with all the stories of Alonso's thirst to be first.
"Sometimes I tell him ‘Fernando, we are here for fun. I’m on holiday here in Dubai, don’t give me this’ and he’s like ‘Yeah we're on holiday but we still need to win’," he said of their karting rivalry.
De la Rosa recalled also a time at Ferrari when Alonso suggested they race at a track near Venice.
After spending all night researching online, De la Rosa realised he had been tricked.
"He took me to a place I hadn’t seen before. I said ‘Fernando there’s no need for this, you were going to beat me anyway.’ He just wants to make sure."
