The two soccer talents have been at the forefront of their sport for many years, trading awards and the title of best player of the year.
F1 fans may not fully agree with the Toro Rosso driver's assessment, with many probably adding Sebastian Vettel, Daniel ricciardo or even Max Verstappen to the mix.
"Hamilton is the Messi of F1 and Christian Ronaldo would be Fernando Alonso, although Christiano wants it all, to win and to be the best," Sainz told Spanish publication Marca.
"Fernando also wants to win, but not both."
Sainz has never denied his admiration for Alonso, considering his countryman as a role model as a young driver.
Now that he's on the grid with the McLaren driver, and even in front of him on occasion, he can get a front row seat , like in last year's US Grand Prix, and see exactly why he compares his talent to the skills of the Real Madrid striker.
"Fernando is a fighter and has so much experience, he's always more difficult to pass than the others. He's an old dog who knows everything".