The 18-year-old striker joined City on a £2 million move from Bursaspor over the summer transfer window but was subsequently loaned out to Belgium side Genk due to work permit issues.
“They had been watching me since U-15 level and really do have an incredible scouting network that operates at such a professional level,” Ünal told the official Turkish Football Federation website.
Ünal also went onto explain the scouting process and how he was first spotted by City.
“Especially at international level if you put on good performances the scouts immediately pick up on this and that is how I first entered their radar, there were other clubs as well but I chose City,” he added.
The Turkish international striker has already opened his scoring account at Genk in the Belgium cup and has played 127 minutes of Pro League football.
Ünal is regarded as one of the brightest talents in Turkish football and became the youngest player to score in the Super League when he netted against Galatasaray in 2013.
Despite being just 18 years of age Ünal has already represented the Turkish national team at senior level.