The two teams meet on Wednesday in the opening leg in Kashiwa, with the ultimate aim to win their first Champions League trophy.
Both clubs advanced to the knockout stage as group winners before coming through their respective last-16 ties with relative ease.
And Nelsinho believes there will be little to separate the sides over the two matches.
"If you look at the results of both teams in the group stages, then you can expect a very tight quarter-final," the Brazilian said on www.the-afc.com.
"It will be a high level game. We know we're going to have our work cut out and we are well aware that we are going to face a tough opponent, but hopefully we can take control of the game."
With the Saudi Arabian season yet to get under way, Al Shabab coach Michel Preud'homme expects his players to be short of their best form.
"We have prepared as well as possible but this is the first official match of the season for us so we are not completely ready," said the Belgian.
"Our preparations have been good but it will be difficult, but we will do our best. It's the same for all of the other clubs from Saudi Arabia in this competition."
Domestic rivals Al Ahli will face a similar problem when they take to the field against FC Seoul on Wednesday.
The Jeddah-based club finished as runners-up in last season's Champions League and will be looking to further impress as Vitor Pereira takes charge for the first time following his move from Porto.
Chinese Super League leaders Guangzhou Evergrande will be looking for Muriqui to continue his form in front of goal, with Qatar's Lekhwiya the visitors to the Guangzhou Tianhe Sport Center.
The Brazilian is the leading scorer in this season's competition with eight goals, and is confident they can go further than the quarters.
"We do not know a lot about Lekhwiya, but I am sure that they are a great team as every team who has reached this stage has good players," said Muriqui.
"Every match in the knockout stage will be great and I am looking forward to competing to become the winner of the AFC Champions League this year."
Two-time Champions League winners Esteghlal face Buriram United in the other quarter-final, with the first leg to be held at Tehran's Azadi Stadium.