Portugal head coach Fernando Santos jumped to the defence of his experienced side after they cruised past Luxembourg 5-0 in their World Cup qualifier thanks to Cristiano Ronaldo.

Ronaldo's 58th career hat-trick and 10th international treble put hosts Portugal out of sight at the Estadio Algarve, where Joao Palhinha and Bruno Fernandes also got on the scoresheet on Tuesday.

The five-goal crushing left Portugal a point behind Group A leaders Serbia, albeit with a game in hand, with two matches remaining and the top two teams meet on the final matchday, in what is likely to be a winner-takes-all decider.

However, Santos' focus after the game was on the age of his squad as he quashed suggestions that his veterans were likely to let him down again, after exiting both the 2018 World Cup and Euro 2020 at the last-16 stage.

"I hear a lot about it [the age of the squad], I even understand, but more changes than what we have been done over the past six years are difficult," Santos told reporters during his post-match his news conference, with set to be 37 heading into next year's World Cup.

"Just look at who was at the World [Cup], the European Championship and who is playing now. There are no age restrictions, it doesn't even make sense.

"Players do not have to stop playing for the national team because they are of more or less age, quality is what counts. 

"Fortunately, we have a lot of 30-year-old or 31-year-old players able to get here and play and the players have shown that [quality]."

Portugal will have to wait until November's international break to seal their fate and Santos appreciates the decisive nature of the Serbia clash while imploring his side to still improve.

"We managed to restrain the opponent and take advantage of every situation to transform them into goalscoring opportunities," he told RTP after the game.

"We did very well until the 25th minute, with how we played and what we had seen from Luxembourg.

"After that we also did well, but we started to want to do everything in a hurry, in one touch, two touches, and we even allowed Luxembourg to get ahead.

"The last game will be decisive, whatever happens in the next round, neither team will be out, although I believe we will win [against the Republic of Ireland] – it will be decisive."