Al Nassr problem is their back line is too fragile, just imagine after Al Nassr scored a goal then Al Ahli was able to counter the attack after that, this shows how bad Al Nassr back line is even though Al Ahli didn't make many shots and only 2 were on target but they could convert them all into goals so it's useless if Al Nassr has good quality in the front line if they don't improve their defense then it will be difficult to fight for the title.
Al Nassr coach is too focused on improving their front line that he hasn't thought about recruiting quality defenders to improve their performance in all areas.
Honestly with Simakan and Inigo, they should normally be pretty good. Maybe they just needed more time to get used to each other, because looking at the current state of the squad, their defense doesn't look that terrible.
I mean at least good enough to beat a team like Al Ahli at least. Jorge Jesus is a great coach too, one that won this league, so they should be able to find a way to make sure that the defense is tight and not giving up positions that easily. I believe they should play a bit low on defense, like be closer to goalkeeper, so that you do not leave any counter attacking chances. Defense itself (not the whole team) should park the bus, and be near their own line ,and that way they can always be ready for an attack.