Yes, I think Al Nassr team is quite strong in the attack department, because Cristiano Ronaldo and Sadio Mane are two experienced players and they can design any attack at any time and succeed in it. But I think the biggest weakness of Al Nassr team is revealed in the defenders, because relying on only one or two players can never guarantee a team's victory.
The responsibility falls on the whole team, but if Al Nassr defenders change the weakness very quickly, then the most needed experienced defender will be Al Nassr team will be able to give good results to the fans at any moment.
Although Al Nassr has Cristiano Ronaldo and Sadio Mane in the attacking line, the team lacks quality midfielders.
In your eyes the defender's weakness is in my eyes the midfielder's weakness they need to improve considerably in these two positions. Strikers don't score goals because of midfielders' failures, teams don't win because of defenders' failures. As this club has enough money, if this club focuses more on their midfield position and strengthens this position as well as recruiting good quality players in defense then I believe this team will definitely be at the top next season.
In my opinion, Al Nassr did the best thing by bringing Cristiano Ronaldo to the team. Of course, they have an effective player like Mane, but football is not played only with attacking players. In football, midfielders and defenders are as important as attacking players. For Al Nassr, these two positions are at an average level. They need reinforcements. If they want to be champions in the Saudi Arabian Pro League, they have to do a detailed study.