Unal, on loan at the Dutch side from City, pounced for a simple tap-in to roll the ball into the back of the net but it served to highlight just what the profligate club is missing at the moment.
The young Turkish international joined NAC over the winter transfer window after an unsuccessful spell on loan at Belgian side Genk.
The 18-year-old striker was forced to leave City on loan after failing to gain a work visa to play in England.
In 2013, aged 16, the wonderkid shot to prominence when he became the youngest player ever to score in the Turkish top flight, finding the back of the net in a match against Galatasaray.
Answer to goalscoring problems under City's noses?
With Guardiola taking over at the Etihad next season he will be keen to make a statement by making some new signings.
But the answer to City's goalscoring problems could be right under their noses in Unal who has been earning rave reviews in Holland.
After scoring 25 goals in 24 games for the Turkey U16 side, Unal was quickly promoted to the U17s, and after scoring his first professional goal in 2013 was invited to join the country's U21 side, despite being just 16 years old.
The player seems destined for great things and there is no better place for him to realise his potential than at the Etihad as he comes from a family of City fans.
The player's father went to Manchester to watch the Citizens on a number of occasions only to see his son sign for the club years later.