Al Nassr were the first of the two in action in Riyadh and produced a real statement of intent by thrashing United Arab Emirates' Al Wahda 5-1.
Abderrazak Hamdallah opened the scoring at Mrsool Park after seven minutes, when he applied the finishing touches to a wonderful team move before Pedro Emanuel's turned on the style after the break.
Three goals inside the opening 15 minutes of the second half -- a brace from Jaloliddin Masharipov and one from Abdulfattah Asiri -- effectively ended the contest, and Sami Al-Najei then added a fifth in the 74th minute.
Ismail Matar pulled one back for Al Wahda in injury-time but it was little more than a consolation, as Al Nassr advanced to the semis of Asia's premier club competition for the second season running to keep alive their hopes of a first title.
Later on Saturday evening, they were joined by compatriots Al Hilal, who remain in the running to be crowned champions of Asia for a second time in three years with a 3-0 win over Persepolis of Iran at the Prince Faisal bin Fahd Stadium.
Salem Al-Dawsari broke the deadlock in the 27th minute with a stunning long-range effort, before Bafetimbi Gomis -- Al Hilal's top scorer in their title-winning campaign in 2019 -- came to the fore with two close-range finishes after halftime to secure his team's progress.