Akram Afif and Baghdad Bounedjah scored for Sadd in their 2-1 victory.
Al Gharafa joined Al Arabi on 10 points with a comeback victory against Al Alhi.
Ahmed Yasser gave Duhail the lead in the 66th minute, but Franck Kom cancelled it 10 minutes later.
Mohamed Benyettou scored a brace as Al Wakrah defeated Al Shahania.
Mohammed Salah Elneel, Aron Gunnarsson, Pierre Michelle Lassogga and Hamdi Harbaoui scored for Arabi, while an Adil Rhaili own goal also contributed to the rout.
Al Arabi, who look a vastly improved side, take on Umm Salal.
Amir Cup champions Duhail take on Al Rayyan in a crucial fixture on Sunday
Al Sadd lead the table with six points from two matches.
Reigning QSL champions Al Sadd look for all three points against Al Shahania.
Al Gharafa lead the table with four points after two matches.
Youssef Msakni had given Al Duhail SC an early lead.
Heimir Hallgrímsson-coached Arabi showed they are a team to watch with a convincing 3-1 win against Al Ahli in the opening round.
The former Ajax and AC Milan midfielder expects to do well with Al Shahania.
Mahmous Almawas scored two beautiful goals to help Umm Salal hold Al Rayyan.
Ahmed Alaaeldin starred for Gharafa with a double.