The result leaves the tie finely balanced ahead of next week’s second leg in Cairo, where the Egyptian club will look to continue their pursuit of a third consecutive continental title and a record-extending 13th overall.
"We faced a strong opponent and missed several scoring chances," Koller said in his post-match comments. "But we prevented them from taking control at home. The tie is decided over two matches, and we still have the return leg."
Ahly deployed a defensive 5-3-2 formation at Loftus Versfeld Stadium, aiming to frustrate Sundowns and capitalize on counterattacks.
The approach largely succeeded, with the South African side struggling to create clear chances.
Koller praised his players for executing the game plan, but warned that focus must remain high heading into the second leg.
"We are well aware of the threat our opponents pose," he said. "We’ll prepare thoroughly to keep them from scoring."
Ahly reached the semi-finals with a 2-0 aggregate victory over Sudan’s Al Hilal and remain unbeaten in this season’s competition.
Sundowns, meanwhile, progressed after edging Tunisia’s Espérance 1–0 on aggregate.
The second leg takes place in Cairo on Friday.
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