The evening ended on a sour note for Al-Hilal when Neymar, who returned two weeks ago from a year out due to a ruptured cruciate ligament, was replaced 29 minutes after his introduction from the bench due to injury.
Ronaldo, making his first appearance in the rebranded Asian Champions League having missed last week's 1-1 opening draw against Iraqi club Al Shorta, had a goal disallowed for a narrow offside at the beginning of the second half.
Al Nassr captain Ronaldo did not travel with the squad for the match in Baghdad, with the club issuing a statement a day before stating that the Portuguese superstar had been diagnosed with a viral infection.
The Portuguese veteran is targeting Asia's top club crown to add to his long list of achievements when the competition kicks off on Monday.
The revamped Asian Champions League Elite will play a crucial role in encouraging fresh investment in the continent's clubs, said the senior-most official of the Asian Football Confederation (AFC) as the body aims to revitalise the sport in the region.
The winners of the new Asian Champions League Elite will pocket a minimum of $12 million, the Asian Football Confederation said on Wednesday in a major boost to club football in the region.
A 2-0 victory at fellow Saudi side Al Ittihad saw them surpass the previous record of 27 straight wins by a top-flight team, set by Welsh team The New Saints in 2016.
The 39-year-old Portuguese was the only Al Nassr player to score in the shootout as his Saudi side went out 3-1 on penalties, the tie having ended 4-4 on aggregate.
Nassr, who won last week's first leg 1-0 thanks to a Ronaldo goal nine minutes from time, were the better side at Al Awwal Park and took the lead on 17 minutes through Portuguese winger Otavio.
Former Liverpool striker Sadio Mane and Anderson Talisca also scored for the Saudi side late Tuesday as they made it three wins from three in the group stages of the premier Asian club competition.
The former Paris Saint-Germain forward, signed in August for a reported 90 million euros ($94 million), grabbed the second in the record Asian champions' win at the Azadi Stadium
Senin Sebai scored on the break to put the club from Dushanbe in front with a minute left in the first half and Istiklol held out under relentless pressure until Ronaldo levelled with a clever clipped finish in the 66th minute.
Cristiano Ronaldo enjoyed a winning debut in the Asian Champions League as he helped Al Nassr to a 2-0 victory against 10-man Persepolis in Iran on Tuesday night.
Neymar, signed last month from Paris Saint-Germain for a reported €90 million, was making his first start for the record Asian champions having debuted on Friday as a substitute in the Saudi Pro League victory at home to Al Riyadh.
The Saudi Pro League side came from behind to triumph 4-2 in the play-off at Mrsool Park, with Brazilian Anderson Talisca scoring twice and Croatia international Marcelo Brozovic rounding off the win. Nassr had been two minutes from exiting the tournament
A club from Bangladesh have been allocated an indirect slot in the upcoming top-tier club competition of the Asian Champions League (ACL), subject to obtaining ACL licensing, confirmed a Bangladesh Football Federation (BFF) official today.