Moemen Zakareya haunted his former club with a well-taken double as Ahly put Zamalek's Egyptian Premier League title celebrations on hold with a 2-0 victory that helped him extend their unbeaten run against their Cairo foes to 20 matches.
The 27-year-old, who joined Ahly after leaving Zamalek last January, opened the scoring on 31 minutes with a superb shot from inside the area before ensuring the win with a beautifully-taken free kick nine minutes from time.
Ahly have not been defeated by their cross-town rivals since slumping to a 2-0 league loss in 2007 after they had already won the title, winning 11 matches and drawing nine since then.
Zamalek needed at least a draw to win a league title that has eluded them since the last of their 11 triumphs in 2004 but looked a pale shadow of the powerful side that have tormented the majority of opponents this term.
They are still overwhelming favourites to win the title as they need only one point from their remaining two games against El-Geish and Wadi Degla.
Ahly, who are now six points behind Zamalek, will cause a huge upset should they win their last two games and Zamalek lose theirs. In this case, they will pip their rivals to the title virtue of a better head-to-head record after the previous derby in January ended in a 1-1 draw.
Zamalek finished with ten men after right-winger Hazem Emam received a straight red card in stoppage time for kicking out at Ahly's youngster Ramadan Sobhi.
Zamalek, looking too cautious in the first half, sat deep and gathered players behind the ball to soak up early pressure from Ahly, who laid siege to their opponents' area albeit without creating clear-cut chances.
The first chance fell to Zakareya after 18 minutes when he was found unmarked by a low cross from playmaker Abdallah El-Saied but his curling shot from inside the area narrowly missed the target.
He made amends one minute past the hour mark after some good work from right-back Basem Ali, one of Ahly's liveliest performers in the first half, having repeatedly exploited the gaps behind Zamalek's right-footer Hamada Tolba, who is often deployed on the left.
Ali darted down the right and sent in a cross that Zamalek's defence poorly dealt with, as the ball fell to Zakareya to neatly control it before blasting a half-volley into the top corner of the net past the despairing dive of Ahmed El-Shennawy.
Zamalek relatively improved in the early stages of the second half, trying to pile on pressure upfront.
However, they still missed the spark of playmaker Ayman Hefni, who was absent due to illness, with winger Mostafa Fathi and lone striker Bassem Morsi finding little support from three central midfielders.
Ahly then regained control, with their intricate passing game leaving Zamalek's defenders chasing shadows. Despite their domination of possession, Ahly looked reluctant to push forward and end the game as a contest.
But a chance to wrap up the win came through a controversial set piece with nine minutes remaining when Walid Soliman was adjudged to have been fouled by Ali Gabr although television replays showed there was no contact between both men.
Zakareya's curling, angled effort sailed over the wall and past the hapless Shennawy as Zamalek failed to lay their derby ghosts to rest.
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