Matlaba suffered a "grade two tear of the hamstring" in Bucs' 1-0 win at CS Sfaxien in the CAF Confederation Cup this past Sunday.
Pirates, via their website, say the Bafana Bafana international will "most likely" sit out the upcoming Soweto Derby at FNB Stadium.
Fellow defenders Rooi Mahamutsa and Patrick Phungwayo are also both nursing Achilles complaints, with the latter replacing Matlaba at Stade Taïeb Mhiri last time out.
However, new Buccaneers signing Gift Motupa has resumed training after shaking off an ankle complaint sustained on international duty.