Ünal joined the Belgium side on a two-year loan after joining City on a permanent £2 million transfer last month.
The 18-year-old has came off the bench for his first few games for the Belgium outfit but made his first start in the league game against St Truiden.
The Turkish forward was part of the City squad that toured Australia over the summer but was sent out on loan due to lacking the necessary work visa requirements to play in England.
Ünal is expected to gain experience in the Belgium league before progressing to the Premier League with his parent club City.
St Truiden v Genk
Kick-Off: 19:30 GMT
Referee: van de Velde J
St Truiden: Dutoit, Rherras, Artabe, Erichot, Bagayoko, Angban, Schoofs, Ono, Paulo da Silva, Mbombo, Dompe
Genk: Köteles, Castagne, Kabasele, Dewaest, Tshimanga, Buyens, Heynen, Buffel, Gorius, Schrijvers en Ünal