Stefano Pioli avoided an embarrassing first defeat as Al-Nassr head coach as Nawaf Bu Washl's 91st minute winner saw the visitors beat second tier Al-Hazem in the King's Cup on Monday.
Pioli, taking charge of his second game of the Saudi Pro League club, saw his side go close to opening the scoring early on when Talisca's effort struck the woodwork.
But Al-Nassr's dominance was rewarded in the sixth minute of first-half injury time when Sadio Mane headed beyond Ibrahim Zaid after Sultan Al Ghannam's cross.
However, the hosts stunned Pioli's side just after the hour-mark as Basil Al Sayyali turned home his second goal of the season with an emphatic finish off the crossbar.
Al-Nassr's frustrations continued heading into the closing stages as Mane, Mohammed Marran and Wesley saw their efforts repelled by their plucky opponents.
But with the game poised for extra-time, a defensive mix-up between Saud Al Rashed and Zaid allowed Bu Washl to steal in, finishing into an empty net to send the visitors into the hat for the next round.
Data Debrief: Pioli feels Ronaldo absence
Without Cristiano Ronaldo within their ranks, Al-Nassr lacked a clinical finisher at the top end of the pitch, failing to capitalise on the opportunities they created.
The visitors ended the contest with an expected goals (xG) total of 3.16, but only eight of their 21 shots were on target, whilst they also missed five big chances.
Mane was the notable standout for Pioli's side, registering more touches in the opposition box (eight) and total shots (five) than anyone for Al-Nassr.