Saad provided an irregular drug sample in July, which he claims resulted from inadvertantly taking a substance alleged to be on the AFL Anti-Doping prohibited list.
The 23-year-old has continued playing AFL while his B sample was returned - but he will now miss St Kilda's two remaining matches, against Gold Coast and Fremantle, after the B sample was reportedly returned postive.
He faces a two-year suspension from the game, though the club stressed this latest action was not an admission of guilt.
"The commencement of the provisional suspension is not an admission of guilt or wrongdoing and the matter will be determined before the AFL tribunal at a date to be fixed," the club said in a statement.
"Saad is not available for selection for the remaining two matches of the AFL home and away season and will continue to co-operate with the AFL and ASADA as necessary throughout this process.
"The club and AFL Players' Association will continue to provide appropriate support to the extent allowed under the Code."