Al-Nassr remain in the third place with 54 points but they are now three points behind second-placed Al-Hilal and seven off leaders Al-Ittihad, who visit Al-Ahli on Saturday.
The 32-year-old former Barcelona and Paris Saint-Germain forward played just seven times for Al Hilal despite a reported salary of around $104 million a year.
Santos' president told Brazilian superstar Neymar it was "time to return to (his) people" in a video published on social media on Tuesday.
"The club expresses its thanks and appreciation to Neymar for what he has provided throughout his career with Al-Hilal, and wish the player success in his career," said a club statement posted on social media.
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.
"Happy to be back in the group," Neymar posted on Instagram, with pictures of him running and kicking the ball, watched by Al Hilal's Portuguese coach Jorge Jesus.
Saudi Pro League champions Al-Hilal battled past Cristiano Ronaldo's Al-Nassr 5-4 in a penalty shootout on Friday to win the Saudi Cup and claim the domestic double, leaving the Portuguese forward in tears at the end of the drama.
Neymar is set to miss the start of the next Saudi Pro League season as he recovers from a serious knee injury, Al Hilal's coach said Tuesday.
Al Hilal, who lost Neymar Junior to injury in October, beat bottom-placed Al Hazm 4-1 to go an unbeatable 12 points clear of Ronaldo's Al Nassr with three matches remaining.
Portugal's record scorer was shown a straight red card four minutes from time for elbowing an opponent when his side were 2-0 down before they scored a late consolation.
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 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
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.
Aleksandar Mitrovic joined the Premier League exodus to Saudi Arabia by leaving Fulham for a club record fee to join Al Hilal on Saturday.
Flame-throwers and a volley of fireworks lit up the Riyadh sky as the flamboyant forward appeared in Al-Hilal's blue kit at Riyadh's 68,000-capacity King Fahd International Stadium
A rock star welcome will await him at the King Fahd International Stadium in Riyadh where he will be unveiled before thousands of fans on Saturday.
The 31-year-old Neymar signed a two-year contract with the Riyadh-based club on Tuesday after spending six years with Paris St Germain, in a deal reportedly worth about 90 million euros ($98 million)
Saudi Professional League (SPL) club Al-Hilal announced that Neymar had signed a contract until 2025, with the Brazilian saying, "I am here in Saudi Arabia, I am Hilali" in a video on the team's social media accounts
The Brazil international joined the French champions for 220 million euros ($241m) from Barcelona in 2017
