Mumbai City FC began their AFC Champions League campaign on a disappointing note, losing 0-2 to debutants Nassaji Mazandaran of Iran, at the Balewadi stadium in Pune, on Monday.
Goals from Ehsan Hosseini (34th minute) and Mohammadreza Azadi (62nd) sealed a comfortable victory for the visiting side in Group D.
In another match in Riyadh, Ali Al-Bulaihi's equaliser 10 minutes into stoppage time spared Al-Hilal's blushes as Neymar made his first start for the Saudi Pro League side in a 1-1 draw with Uzbekistan's Navbahor.
Saudi Arabia international defender Al-Bulaihi rose to meet Brazilian winger Michael's centre to cancel out a Toma Tabatadze strike in the 52nd minute of the Group D meeting that had looked set to earn Samvel Babayan's side an unlikely win.
In Pune, Mumbai made a bright start and almost opened the scoring in the ninth minute when Jorge Pereyra Diaz slipped the ball through to Lallianzuala Chhangte, but the latter’s shot from a tight angle missed the target.
With 11 minutes left in the half, Nassanji took the lead. Hossein Zamehran took possession of the ball 20 yards from goal and, with a defence-splitting pass, fed Ehsan Hosseini, who slotted calmly into the bottom corner of the net.
Bipin Singh could have drawn Mumbai level with a minute to go for half-time but was off target after being put through by Chhangte across the face of the goal.
The Iranian outfit consolidated their led when substitute Farshid Esmaeili robbed Akash Mishra deep inside his penalty area and had the presence of mind to roll the ball into the six yard box for Azadi to score.
Vikram Partap then shot across the face of goal and Chhangte glanced his header wide as Mumbai sought a late lifeline but Nassaji saw out nine minutes of additional time to taste victory in their maiden AFC Champions League appearance.
Late header salvages draw for Al-Hilal
Neymar, among the headline arrivals in Saudi Arabia over the summer, was included in the starting line-up for the first time since his 90 million euro ($96 million) move from Paris St Germain but was frustrated throughout the encounter.
The Brazilian looked like he would end up on the losing side until Al-Bulaihi's header, which came during more than 14 minutes of injury time, finally put an end to Navbahor's determined resistance against their expensively-assembled opponents.
Only the winners of the 10 groups in the 40-team competition are guaranteed to advance to last 16 and Al-Hilal sit behind debutants Nassaji Mazandaran in the early standings.
The Iranians top the group after the 2-0 win over Mumbai City.
There were no such problems for Saudi Pro League champions Al-Ittihad, who cruised to a 3-0 win in Group C over AGMK from Uzbekistan despite coach Nuno Espirito Santo not including ex-Real Madrid striker Karim Benzema in his squad.
Haroune Camara gave the former champions the perfect start in Jeddah in the 11th minute when he slammed home after goalkeeper Botirali Ergashev's save and Romarinho doubled the lead four minutes later with a cool close-range finish.
The Brazilian hit the third three minutes before the interval from the penalty spot after Abderazzak Hamdallah had been fouled in the area by Dilshodbek Akhmadaliev.
Al-Ittihad lead the table after Air Force Club shared a 2-2 draw with Sepahan from Iran, with 19-year-old Ali Jassim scoring twice for the Iraqi side in Erbil.
Meanwhile, Nasaf from Uzbekistan secured a late 1-0 win over Jordan's Al-Faisaly to top Group B ahead of Qatar's Al Sadd and Sharjah of the United Arab Emirates, who shared a 0-0 draw.