Tiatia will also be without Wales prop Rhodri Jones, who suffered a calf injury during the warm-up in Cape Town, while Jarred Rosser tore a chest muscle in a tackle.
Dragons must pick up a point against Bulls, who are already guaranteed a home semi-final in the play-offs, if they are to avoid equalling the worst URC league season.
Zebre currently hold that record after claiming just nine points in 2021-22.
“It’s one final push,” added Tiatia. “It’s the last game of the season, the environment that we’re going to in Pretoria is a challenging place.
“They are second in the league, they are playing a dominant style of rugby, which is the Bulls’ DNA.
“So we’re under no illusion on the challenge and we want to finish strongly with the young players that are here.”
