#3 Karim Rekik — 16 years 09 months 19 days
In 2011, Manchester City and Feyenoord had to go through a few red tapes to settle a deal for Karim Rekik. The 15-year-old was a hot property on Manchester City's wishlist. However, the Dutch team wasn't ready to let go of one of their finest gems.
Eventually, the versatile defender joined Cityzens with hopes of a bright future. He made an unofficial debut in Manchester City's 2011 pre-season outing. Karim Rekik's official debut was marked against Birmingham City in the third round of the League Cup (now EFL).
Rekik continued to impress and eventually earned a senior team contract. Nevertheless, immense competition from senior players in his desired positions meant Rekik had to settle for bench-warming. He moved around in various loan spells for more playing minutes.
After signing for Marseille and then Hertha, Rekik became a Sevilla player in 2020.
#2 Paul Simpson — 16 years 02 months 06 days
Paul Simpson came under the limelight in the modern era after taking charge as England U20 coach in 2017. However, if we roll back a few years, we could also learn that Paul Simpson was the Cityzens' second-ever youngest debutant.
Aged 16, Simpson appeared for the first time in the City kit in a 3–2 win against Coventry City. The event took place on 2 October 1982. Following the team's relegation the same year, the winger was sent out on loan.
He returned as a much more experienced and complete player. Paul Simpson took no time to cement his position at Maine Road. He left City in 1988 for Oxford United.
#1 Glyn Pardoe — 15 years 10 months 16 days
Glyn Pardoe spent his entire playing career with just one club. Between 1962 and 1976, Pardoe remained a crucial player within the ranks of the club. It all started in 1962 when a 15-year-old Glyn Pardoe was approached by Everton and Manchester City.
At the age of 15 years and 314 days, Pardoe made his first team debut. It came in April 1962 against Birmingham City and he became the youngest ever player to feature for Man City. Even today, the record stands.
His services were demanded by the senior and youth teams. Glyn shuffled between both the sides and thus, his reputation within the club and England kept growing. The versatile defender faced a horrendous injury in 1970 and spent another two years in recovery.
He returned in 1972 and retired four years later.