The visitors were leading 2-1 until stoppage time when Aluminum's Mohamed Abdul-Kader secured a share of spoils.
"We were close to claiming a win but the players were too lazy with few minutes remaining, giving Aluminum the opportunity to equalize," Mansour told the club's website.
"We were in desperate need of victory to continue competing for the league title but the players couldn't hold on to their lead."
The players' faults were also apparent in the first-half, according to Mansour.
"They lacked concentration and gave away possession far too often. At the end we were held to a draw that did us no favors."
Zamalek are fourth in the league table 21 points, five behind leaders Al-Gaish, who have a game in hand.
The Cairo giants' hopes to win their first league title since 2004 are gradually fading.