With the junior team, he played in the Spanish Club Championship in which he averaged 15.8 points, 7.2 rebounds and a PIR of 19.2.

On December 27, 2021, he made his debut in the Liga ACB in a match that would end with a 83–100 victory against CB Gran Canaria,[4] in which Mestoğlu would play 42 seconds in which he would provide an assist.

[8] On 26 January 2024, he suffered an injury during Fenerbahçe Beko's team training for the Virtus Bologna match in EuroLeague.

[9] After the checks, a right knee anterior cruciate ligament tear was detected and surgery was performed on 1 February 2024.

[10] After an eight months rehabilitation period, he was back to court with Fenerbahçe Koleji Novotel and scored nine points against Harem Spor (lost 88–66) on 1 December 2024[11] and scored 17 points against Çağdaş Bodrumspor (won 119–112) on 4 December 2024.