A stoppage-time penalty from Kaveh Rezaei gave Iranian hosts Esteghlal a 1-0 advantage over Al Ain as both sides finished the first leg of their AFC Champions League last-16 tie with 10 men.
An uneventful contest began to unravel in the 77th minute when the visitors from the UAE had Saeed Juma dismissed for a two-footed tackle on Mohsen Karimi.
Esteghlal's numerical advantage was short-lived when Farshid Esmaeili retaliated to a challenge from Al Ain winger Caio.
But Alireza Mansourian's men were able to take an advantage into the return leg after Mohammed Ahmed handled in the box when he misjudged a clearance and Rezaei sent goalkeeper Khalid Eisa the wrong way.
Two-time runners-up Al-Ahli of Saudi Arabia played out a 1-1 draw at home to their namesakes Shabab Al-Ahli Dubai.
The away side went ahead through Khamis Esmaeel after Yasser Al-Mosailem punched poorly from a 20th-minute free-kick, although Abdulfattah Asiri latched on to Mohamed Shafy's pass to level seven minutes before half-time.