Letlotlo is due to have surgery on Friday after rupturing his anterior cruciate ligament in training.
'Letlotlo hurt his knee during training,' Chiefs confirmed on their website.
'He will undergo surgery, which is scheduled for Friday.'
Letlotlo was hoping to build on the two starts and three substitute outings in the league he managed in 2016/17 following his promotion to the first team.
Amakhosi also have Gustavo Paez, Bernard Parker, Ryan Moon and Michelle Katsvairo as other options upfront.