The Sebokeng-born midfielder spent this season playing in the ABC Motsepe League after he was demoted to Pirates' feeder team Pele-Pele.
Mahlonoko made history in 2018 when he became the club's youngest ever PSL debutant as a 16-year-old in the colours of the Mighty Buccaneers.
10. Oupa Manyisa made his Pirates debut aged 20 years and 1 month against Golden Arrows on 30 August 2008
9. Happy Jele made his Pirates debut aged 19 years 8 months and 19 days against Maritzburg United on 20 September 2006
8. Tlou Segolela made his debut aged 19 years 5 months and 16 days against Moroka Swallows on 15 August 2007
7. Excellent Walaza made his debut aged 19 years 5 months and 12 days against Maritzburg United on 20 September 2006
6. Siphumelele Mbulu made his debut aged 19 years 4 months and 11 days against Free State Stars on 14 May 2018
5. Andile Jali made his debut aged 19 years 3 months and 30 days against Ajax Cape Town on 09 August 2009
4. Thabiso Monyane made his debut aged 19 years 3 months and 4 days against Bloem Celtic on 3 August 2019
3. Senzo Meyiwa made his debut aged 19 years 1 month and 15 days against AmaZulu on 8 November 2006
2. Lyle Foster made his debut aged 17 years and 12 days against Maritzburg United on 15 September 2017
1. Augustine Mahlonoko made his Pirates debut aged 16 years 11 months and 18 days against Highlands Park on 4 August 2018
The 18-year-old midfielder was also voted amongst the top 60 young talents across the world in the same season.
According to a source close to Pirates, 25-year-old midfielder Yusuf Maart also faces an exit from the club.
"Augustine has left Pirates. He got his clearance last week," the source tells KickOff.com. "Yusuf is also set to leave but nothing is yet confirmed with him."
Mahlonoko preferred not to comment about his future and referred us to his agent Keke Mokoena, who declined to comment.
Efforts to get hold of Bucs administrative official Floyd Mbele proved futile after he failed to pick up our calls.