Esteghlal lost to Al Sadd 2-0 in Doha’s Jassim Bin Hamad Stadium.
“They scored the first goal due to a mistake by our goalkeeper. In the second half, we tried to reduce the difference, but we paid for individual mistakes,” said Nekounam.
“We knew it would be a difficult match because we faced a very tough opponent. Al Saad performed well but on the other hand, we made many mistakes that led to this result,” he added.
Next up for Esteghlal are Saudi Arabia's Al Nassr at Tehran’s Azadi Stadium on October 22.