To make matters worse for Mansourian, Al Ahli were just one of two teams to go undefeated during the group stage of the AFC Champions League.
Even though Al Ahli dominated their competition throughout the group stage, Mansourian is confident that his side can hand the Saudi Arabian club their first defeat of the tournament and also take one step closer to reaching the quarter-finals.
"We know them quite well, they are a very strong team," Mansourian told reporters on Tuesday. "First of all we will try not to concede a goal, then try to score. If we can score more than two goals, it will be great.
"We have studied every single player from Al Ahli and know them quite well. When we play in the continental arena, we are no longer considered Naft of Tehran, but we are Naft of Iran."
Mansourian added that his side's spirits will not be at rock bottom heading into the match after they failed to clinch the Iran Persian Gulf League title.
Naft Tehran had to beat Tractorsazi in the final match of the domestic season to be crowned champions, but failed to do so as their match ended as a 3-3 draw.
As a result of that, Sepahan beat both teams to the title as they defeated Saipa 2-0 to finish one point ahead of Naft Tehran and Tractorsazi.
"The fact that we lost the Iran league trophy in the last few minutes has not affected us and our incentives and we will do our best to display a good performance," Mansourian said. "I am proud of my players. They are very young and have great motivation to play in the knockout stage of the Champions League."