The result, coupled with Jordanian team Al-Wehdat's stunning win over Al-Nassr of Saudi Arabia in the other Group D match, means the Qatari team leads the standings with 10 points going into the final matchday against Al-Nassr, who is second on eight points.
Foolad's hunt for top spot, however, came to an end although the Iran side can still advance if it finishes among the three best second-placed teams.
Nam Tae-hee rose high to head home Al Haydos’ curling cross to end the stalemate in the 65th minute.
The Korea Republic player then almost turned provider in the 69th minute when Mohammed Jadoua headed in his cross but to Al-Sadd’s dismay, the effort was ruled out for offside.