HOUSTON, United States (AFP) — Cristiano Ronaldo is preparing for his sixth World Cup as if it was his first, said Portugal coach Roberto Martinez as he hailed the 41-year-old as "an example and a reference for football." Armed with a richly talented generation, Portugal are among the favourites to win the World Cup for the first time. Ronaldo's continued presence in Martinez's team has sparked debate over whether he is still a positive influence. No one can match the five-time Ballon d'Or winner's 143 international goals.