Setephano (23) joins a growing list of injured Otago loose forwards, with Eben Joubert, Craig Newby and Alando Soakai also unavailable.
It is hoped Newby (sore neck) will be available for the first game of the Air New Zealand Cup against Southland on August 2, while Joubert (broken finger) is likely to be ready the next weekend against Canterbury.
Soakai is to have a shoulder reconstruction and will not play again this season.
Coach Steve Martin has brought Heriot loose forward Sean Tauti into the squad.
He is expected to get a hit-out against Wellington in Wellington on Friday afternoon, in the side's final warm-up game.
Setephano, who injured his calf in the Super 14, was captain of the Otago side which lost a pre-season game to Southland on Saturday.
Martin had yet to decide on a new captain.
He said with the injuries it was obviously not a great build-up but that was the predicament and everyone had to get on with the job.
Tait had played in the Otago trial last month and impressed as a rugged country flanker, Martin said.
Tait deserved a chance as the side looked for an openside flanker, though Martin said Newby could play in that position, if needed.
Martin would name the team to play Wellington today.
