Joao Mario insists Portugal's Sporting CP stars are focused on their World Cup opener against Spain, although he warned his team-mates not to head to Serie A if they depart the crisis club.

Sporting have been at the forefront of the news in Portugal in recent weeks, with fans clashing with players as the team missed out on Champions League qualification and lost the Taca de Portugal final.

Coach Jorge Jesus has departed for Al-Hilal, while there are now reports that a number of key men - including Portugal internationals Rui Patricio, William Carvalho, Bruno Fernandes and Gelson Martins - are seeking to have their contracts rescinded.

Joao Mario, a former Sporting midfielder, is confident that the ongoing situation will not affect the team in Russia, but he did have some advice for his team-mates.

"Serie A is out of the question [for them]," he told a news conference, having endured a difficult time with Italian giants Inter.

"But this is not a topic for now. The whole group is focused on what's important: the game with Spain. Most of the players are at the World Cup for the first time and that's a big motivation for all of us.

"All other matters are for after the World Cup."

As well as the under-pressure Sporting contingent, there will be plenty of focus on Cristiano Ronaldo against Spain.

The Real Madrid man has suggested he could leave the European champions this off-season, but Joao Mario is confident that the five-time Ballon d'Or winner is ready to deliver for his country.

"We have to be at our best against Spain. I'm sure the whole team will make a great showing - not just Cristiano," he said. "Portugal versus Spain is always a special game.

"Cristiano Ronaldo is the best player in the world and he will be the star of this World Cup. There are no words to describe him."