The AFL confirmed on Friday night the Saints had withdrawn Trent Dennis-Lane from their emergency players for Saturday's match at the Gabba and replaced him with Saad.
Saad was named on Wednesday as being under investigation by the AFL for an alleged breach of the anti-doping code for taking a substance permitted for use "out of competition."
Until the sample results of both tests have returned, no action can be taken and Saad is eligible for selection.
An AFL spokesperson said the League was yet to receive the results of the second sample.
If charged, Saad would face an AFL Tribunal hearing and, under the anti-doping code, use or possession of a prohibited substance can lead to a two-year ban for a first violation.
The small forward has played 12 games this year for 15 goals, but was not named for St Kilda or VFL affiliate Sandringham on Thursday when teams were announced.
Saad hasn't played in the Saints' AFL side since the round 15 game against Fremantle, although he has played VFL football since.
Coach Scott Watters would not comment on the 23-year-old's welfare on Friday morning.
"I'm not willing to discuss how one of our players is feeling right at the moment," Watters said.
