Ahly were handed their first defeat of the season after slumping to a 2-1 Egyptian Premier League loss to Arab Contractors, courtesy of a controversial second-half penalty.
It was an enticing clash that saw Arab Contractors, the league's highest-scoring team, take the lead through Mohamed Farouk after just four minutes before Amr Gamal drew level 12 minutes later.
But a second-half controversy saw the referee dismiss Egypt defender Wael Gomaa and point to the spot after he allegedly felled a one-on-one Mohamed Salem – even though the tackle looked outside the box.
Mohamed Adel smashed home the ensuing penalty on 57 minutes to hand the hosts their first win over Ahly since their famous 2-1 victory in 2004's Egypt Cup final.
Egypt forward Mohamed Nagy 'Gedo' made his returning debut in the game after replacing the ineffectual El-Sayed Hamdy in the second half.
Although the defeat ends Ahly's four match winning streak, they still remain in charge of Group A on12 points, with Contractors climbing into third place, one point adrift of the Reds.
The match got off to a thrilling start when Contractors surprised Ahly with the lead early on, thanks to a magnificent effort from midfielder Farouk.
Farouk latched onto an incisive through pass as he sold both defender Ahmed Nabil 'Manga' and keeper Sherif Ekramy a sublime dummy before turning and slotting home with his left foot.
Ahly replied to Contractors' goal with another beautiful effort on 16 minutes, when young forward Gamal superbly eluded a defender before unleashing a powerful left-footed strike that beat keeper Mohamed El-Akabawy at the near post.
But the 25-year-old Farouk came back to daunt Ahly once again, this time forcing a brilliant save from Ekramy after cutting inside his marker to hit a strike that was tipped over by the keeper three minutes from time.
Action began in the second half when a through-on-goal Mohamed Salem was fouled by defence stalwart Gomaa who was handed a straight red card in what seemed to be a harsh decision by the referee.
Rubbing salt in the wound, the official also pointed to the spot, allowing Adel to restore Contractors' lead.
Ahly then poured forward as the Mountain Wolves sat deep to defend their narrow lead and the African champions could have scored when a Trezeguet thunderbolt went narrowly wide off the bar on the hour mark.
Keeper El-Akabawy came to his side's rescue when he thwarted a close-range sitter from the lively Gamal five minutes later, as the Cairo giants tried incessantly to find a breakthrough, albeit to no avail.
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