The Serbian defender spent three years with the Blues, playing in the 2013 FA Cup final and winning a Premier League champions medal in 2014.
A highly-rated centre-half, Nastasic was just 19 when he joined the Blues from Fiorentina in the summer of 2013 and quickly became a popular figure among the City fans.
He made his debut in a dramatic 3-2 defeat to Real Madrid in the Bernabeu and went on to play 30 games during his first full campaign and was voted the Club’s Young Player of the Year.
READ: Kevin De Bruyne | ‘Back and ready to roll!’
WATCH: Every Angle | Gabriel Jesus’ sublime second
GALLERY: Tuning up for Leicester
He played another 20 games in the title-winning 2013/14 season but was ruled out with injury for several months and never really regained his place thereafter.
He moved to Schalke on loan in January 2015 and transferred to the Bundesliga side permanently at the end of the campaign.
In total, he made 51 appearances for the Blues.
Still only 25, Nastasic has clocked up 99 appearances for Schalke and won 27 caps for Serbia to date.
He admits drawing City in the Round of 16 was a bit of a shock but is delighted to be playing a club he still has a great deal of affection for.
“I have to be honest, I didn’t expect that we would be playing City, but when I saw the draw I was really happy because I will come back to Manchester and see some old faces,” said Matija.
“When I was in City, I was really young. In the beginning it was perfect for me but at the end, not so successful.
“But I have to say I enjoyed every day I was with the Club and I am proud that I was part of Manchester City.
“All the people who worked and still work at the club were fantastic and professional.
“I am really looking forward to playing again at Etihad because I had some great memories there and I can say only good things about the Club.”
Nastasic says Schalke will aim to make home advantage count and also added that former Schalke favourite Leroy Sane is assured a warm welcome on his return.
“Leroy is great player and person and he is always welcome in Gelsenkirchen and this time will be no different,” he said.
“We all know how strong City are, so we have to be on our best if we want to do something.
“But at our stadium we have a great support every game and that will be to our advantage.”
