Actually since last season defence is the main weakness of Al Nassr, but strangely enough they don't seem to see this position to be improved, actually Al Nassr has a very dangerous attack line but without the support of a strong defence it will not have a positive effect on their game, currently their performance has actually improved greatly when in the hands of Pioli, but it looks like Pioli still must to improve their defence in the transfer market later, besides that Pioli currently has to emphasize the mentality, focus and concentration of his players to be even better so that they can maintain excellence until the game ends.
I did not follow up their transfer activities in the summer and didn't know that they bought new defenders to improve their defense system or not. It seems they did because when I watched highlights of their matches in this season, I saw new players, and some new defenders like one or two in their squad. But these players failed to help them improving their defense and if Al-Nassr want to have improvements, they will have to buy new players for their club in a next summer transfer season, or if they're hurry, they can try in winter transfer season.
One theory about Cristiano Ronaldo is he is trying to get Al Nassr improved and achieve some title with this team because since he started playing there he couldn't get anything which is not good at all for a player like Ronaldo. He also wanted to win the World Cup title with his country but we can't forget about his age and we can't forget that since Ronaldois getting older he is getting weaker.
Maybe he will get retired in Al Nassr but the other theory about Ronald is he is in Saudi Arabia for money and he is joining another team after Al Nassr to earn more.
He is a very ambitious player and he does not feel comfortable by ending a season as a runner up. It's worse in this season as Al-Nassr now are falling deeper in Saudi Professional League, and chance for them to win Saudi Professional League is almost zero. There is big risk that they can lose their third position too and it will be nightmare and very disappointment for Cristiano Ronaldo.
Even Cristiano Ronaldo is unsure about his future with Al-Nassr. No signal that they will sign a new contract with him and Cristiano Ronaldo might return to Europe with a latest call invitation from Jose Mourinho.