Catrakilis has been diagnosed with an hyperextended elbow, and has been sent back to South Africa for further scans and rehabilitation.
The PE-based franchise accounced on Monday that the experienced Howard Mnisi, who previously played for the Emirates Lions, will join them in Glasgow for their remaining two tour matches in Europe.
Isuzu Southern Kings interim head coach Robbie Kempson believes losing Catrakilis was a massive loss for the team.
“Dimitri is a massive loss for us, especially with all that experience," said Kempson.
"He will travel home and then we will know exactly how bad the injury is. At the moment we are looking at about three weeks and we are hoping it is just that.
“But certainly he is a big loss for us from a leadership point of view, what he brings on the field and his influence on the team off the field as well.
“It does give maybe one or two other guys an opportunity but to lose Demetri doesn’t help our cause for the rest of the tour going forward. There are opportunities for guys like Siya Masuku and JT Jackson to perhaps get an opportunity
“We wish him all the best and hope the injury is not as bad as it looked when he went off the field.”