By reigning World Player of the Year Cristiano Ronaldo's high standards, he's actually had a relatively slow start to the 2017-18 campaign.

The forward was given extra time off after his Confederations Cup exploits and he then received a five-match domestic ban for pushing the referee in Real Madrid's Super Cup win at Barcelona.

Ronaldo has scored five goals in seven games so far this season, but he was yet to find the back of the net in La Liga heading into a very important international break for his national team.

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Portugal, who are by no means assured of 2018 World Cup qualification, travelled to minnows Andorra on Saturday night needing a win, with Switzerland beating Hungary 5-2.

With the Euro 2016 winners behind the Swiss in Group B, it was incredibly surprising that their captain Cristiano was left out of the starting XI - but his manager has explained the reason why.

Cristiano starts Andorra game on the bench

Ronaldo was dropped to the bench and watched on from the sidelines as Portugal dominated possession but failed to convert any of their chances in the opening period.

The 32-year-old came on for Gelson Martins at the start of the second half and 17 minutes later he did what all the best players seem to do - step up when their team needs them the most.

The Real superstar produced a neat first touch inside the box and close-range finish to fire Portugal ahead, and it was his cross that eventually led to Andre Silva's 86th-minute goal.

Why Santos dropped Cristiano against Andorra

After the 2-0 victory, Portugal manager Fernando Santos explained why he left his main man on the bench in Andorra, claiming that a lack of fitness and training was behind his decision.

"I thought a lot," Santos told RTP, via Goal. "I thought, well, (Cristiano) Ronaldo did not train 100 per cent in two of the days of work (prior to the match).

"There were many factors that led to this decision. Games are complicated, I tried to manage and do what was best. Whether it was questionable or not... we ended up winning and that's what matters."

After admitting that his side lacked momentum and found it tough to adapt to the pitch, the 62-year-old added: "I had to put Ronaldo on the field, another forward and everything improved.

"There was a period of adaptation, but from a certain moment we created situations. We ended up winning as well, as we wanted."

Is there another reason?

Another probable reason why Cristiano didn't start in Andorra is the fact that he was one yellow card away from being suspended for Tuesday's huge final group game.

Portugal host Switzerland in Lisbon next week in a clash that will ultimately decide who secures the sole automatic qualification spot in Group B.

With Lionel Messi in serious danger of not being at next summer's World Cup due to Argentina's continued struggles, Cristiano will not want Portugal to suffer a similar fate.

How reliant do YOU think Portugal are on their talisman Cristiano? Can YOU imagine a World Cup without both Cristiano and Leo Messi? Share YOUR thoughts in the comments box below!