Al-Ahly wasted many good scoring chances to grab a precious away goal but were held 0-0 away at Guinean champions Horoya in Friday’s quarter-final, first leg match.
The Egyptian giants were guilty of wasting some good opportunities and will host Horoya next weekend, fearing that an away goal by the Guineans could hurt them.
Having frustrated 2016 champions Sundowns in Pretoria too, Horoya could be fancying their chances when they travel to Cairo for the return leg next week.
Al-Ahly substitute Salah Mohsen missed two clear-cut chances, first being denied by Horoya goalkeeper Germain Berthe in a one-on-one situation, before narrowly missing the target after being set up by Moroccan striker Walid Azaro.
Earlier on, Malian defender Salif Coulibaly and winger Islam Mohareb came close. Horoya defender Abdoulaye Camara had a busy day against Al-Ahly’s attacks, while Daouda Camara hit the side net in a rare chance that came the hosts' way.
Horoya could feel hard done by after Niger international midfielder Mohamed Wonkoye had a penalty call turned down in the second half.
Diomande beat Wydad goalkeeper Yassine El Kharroubi to score from close range 16 minutes into the game.
Given Setif’s inconsistency in the group stages, Wydad were largely tipped to continue with their good form past the Algerians.
But Setif showed some resistance, handing themselves an advantage ahead of the second leg away in Morocco next week.
Wydad will now need to beat Setif with a two-goal margin to progress to the semifinals, while the Algerians would need an away goal for security and avoid limiting a defeat to just one goal.
Winger Ismail El-Haddad was promising for Wydad, as he produced some fine moves but his efforts were fruitless against the stubborn hosts.
Despite being ahead, Setif did not sit back but searched for a second goal with striker El Habib Bouguelmouna and Abdelmoumene Djabou a constant menace for the visitors.