Cristiano Ronaldo has not been affected by Juventus' recent struggles, insists Portugal head coach Fernando Santos. 

The Bianconeri were eliminated from the Champions League in the last-16 stage by Porto a fortnight ago, going out on away goals after the tie finished 4-4 on aggregate after extra time at the Allianz Stadium.

Former Juve boss Fabio Capello singled out Ronaldo for criticism, while ex-president Giovanni Cobolli Gigli suggested the club should never have spent €100million to sign the forward in 2018.

Andrea Pirlo's side bounced back from that defeat with a 3-1 win over Cagliari in Serie A, but their hopes of securing a 10th consecutive Scudetto were left in tatters at the weekend following a shock 1-0 home loss to Benevento. 

Ronaldo, who has been linked with moves to former clubs Real Madrid and Manchester United, has since joined up with the Portugal squad for their World Cup qualifiers against Azerbaijan, Serbia and Luxembourg.

And Santos says has no concerns over the 36-year-old's morale. 

"We've always been close to each other, very good friends, we don't really have a coach-player relationship," Santos told a media conference.

"Ronaldo certainly represents great quality; he always shows great happiness and joy when he's with the team.

"He's an important player, probably the best in the world. I don't think he has any problem in terms of mentality at the moment."

Portugal are red-hot favourites to progress from Group A, which also contains the Republic of Ireland, but Santos insists they will not be complacent as they bid to book their place in Qatar in search of a first-ever World Cup triumph. 

“We mustn't underestimate anyone," he added. “We know Azerbaijan can be quite dangerous on the counter-attack.

"We know Ronaldo always wants to conquer new trophies, but all the players want to win the World Cup. We can fight to become world champions."