Santos' Seleccao take on the Three Lions in a friendly on Thursday and, with captain Wayne Rooney leading young talents like Marcus Rashford, Dele Alli and Harry Kane into the summer showpiece, the Portuguese coach believes Roy Hodgson's men have a chance of glory.
"I've seen England play," Santos said. "They have talented players and they can win in France. England have big ambition, they are one of the favourites.
"They are one of the strongest teams in the world, both with individual quality and teamwork. The manager is very clever and it will be a tough match.
"We need to win in France, so it is not mandatory to win against England on Thursday, but there will be a fantastic atmosphere on Thursday and it's an important match, as we are representing Portugal."
Santos was also asked about his own team's Euro 2016 chances after new Manchester United manager Jose Mourinho said Portugal are among the five teams that can win the tournament.
"Jose is an extremely ambitious coach like me, and he knows the value and the potential of the Portuguese team," he said. "His words are good, but we already expected that from him - a champion."
But Santos is relishing the opportunity to see how his side copes in absence of their 31-year-old star.
"All my players are important," said Santos. "Portugal are not a one-man team and I want to test my whole squad.
"Ronaldo said he played 4,000 minutes this season but when they booked this match, we didn't know he would be playing in the Champions League final.
"Of course he's very important, like he would be for any other team in the world, but this is a good opportunity to play without him. I hope he will play seven games in France but we need to know how to play without him.
"All my players were tired and they have to rest physically and mentally. I'm not worried about this, because we are having good preparation."