Nassir signed with Sundowns early this year but was quickly loaned back to his former club Ethiopian Coffee S.C in Addis Ababa.
The 22-year striker started training with the Brazilians today after being spotted at the Royal Marang Hotel undergoing paces with the rest of his new teammates.
New signing Abdelmounaim Boutouil is still yet to join the team after signing from SCC Mohammedia recently.
"Yes its him (Abubeker Nassir). He is here but for now, the media is not allowed to take photos or talk to him,” said an official at Sundowns.