Yemen will be buoyed by their 2-1 victory over Japan in the final Group D match and will aim to emulate that performance against their neighbours at MHSK Stadium on Sunday.
"We are highly motivated for the match especially after our win against Japan," said Al Nash.
"We respected Japan but we knew that we will have a good result and that’s what happened."
Al Nash, however, will aim to keep his players’ feet on the ground to avoid complacency in order to secure the victory which will earn a place in next year’s FIFA Under-17 World Cup.
"We had high spirits after defeating Japan but we must not think a lot about that match as over-confidence could have a negative affect on our young players," he added.
"The game tomorrow will be important because we want to reach the World Cup.
"Saudi Arabia are a strong team and they will also fight to qualify to the World Cup finals."
Defender Ahmed Al Khamri received two yellow cards in the preliminary stage and will sit out the match through suspension.
However, Al Nash believes he has the players to make up for Al Khamri’s absence.
"Al Khamri is a key player for us in the defence and we will try to cover the gap that he will leave," he said.
"He is an important player but we have good replacements for him.”
Saudi Arabia’s Brazilian coach Joaquim Filho is not underestimating the size of the task which awaits his side. Filho maintains the contest will be difficult to call as the sides know each other so well.
"Yemen are a strong team as they fight until the final whistle and the game will not be easy for us because we are considered as rivals and it will be very hard to know who will win," he said.
"We played against Yemen twice before the competition and we defeated them in one match 4-0 and had a 1-1 draw.
"However, the match on Sunday is going to be totally different."
Filho revealed that defender Motaz Hawasawi is out for three weeks due to a ligament injury while midfielder Nawaf Al Ghamdi is doubtful with flu.
"Hawsawi had an MRI scan yesterday and he will be out for three weeks due to a tear in the ligaments," said Filho.
"Al Ghamdi has flu and we still don’t know if he will be available for the match.
"We have to find replacements for them and we must try to lift the morale of the players and work on the psychological side because this match is important as the winners will qualify to the World Cup next year."