Despite putting in several impressive saves throughout the match, the Cameroonian mistake allowed Youssef En-Nesyri’s strike to stand as the match-winner, handing the Black Sea Storm their first defeat of the season.
Trabzonspor faced an uphill battle after Okay Yokuslu was sent off in the 20th minute for violent conduct, reducing the team to 10 men.
The goalkeeper had initially kept Fenerbahce’s attacks at bay, but in the 45th minute, he misjudged a tame long-range effort from his former teammate Fred, spilling the ball into the path of Sebastian Szymanski.
The Cameroon international managed to block Szymanski’s follow-up, but the rebound fell kindly to Youssef En-Nesyri, who calmly tapped the ball into an open net.
Trabzonspor will face Gaziantep in their upcoming league fixture, which will also mark Onana’s home debut at Akyazi Stadium.