Long known for dousing his hair with gel, Ronaldo hopes to be part of a team that jells into a world champion. He helped the Portuguese reach the semifinals in his first World Cup in 2006 and led Portugal to its first major title at the European Championship two years ago in France.

If Portugal wins its group and Argentina is second — or if Portugal is second and Argentina first — Ronaldo and Messi could even face each other in the final.

Could Ronaldo stay at a high level long enough to play in a fifth World Cup in 2022?"His physical capacity, his technical prowess, his strategy, he's always evolving," Santos said, "contrarily to the regular players."