Cristiano Ronaldo is the greatest clutch player of all time, there's no doubt about his greatness to bring things out of dead situations with his magical moments. He has done so many times and recently did for Manchester United by scoring a last minute equaliser against Atalanta.
Portugal has relied heavily on Ronaldo during this qualifying phase and would need him once more and he also has to fulfil the ambition of playing at the World Cup and would want an easier route to qualify through to Qatar.
Serbia and Portugal are tied on points but Portugal are ahead on goal difference. The two will face off in Lisbon tonight. While a draw is enough, playing to get a draw could be risky and Serbia could do an upset so a win would be Portugal's target.
Ronaldo is Portugal's main goal scoring outlet having scored over 110 goals for the country which makes him the highest scoring international player. He would need to add to his goal tally tonight, while Portugal have other talented attackers, no one does it like Ronaldo.