“Sam’s knee had shown encouraging signs of improvement over the last two weeks,” Adelaide's Science and Medical Services Coordinator Steve Saunders told afc.com.au.
“Unfortunately, Sam is still presenting with meniscal symptoms that have prevented multi-directional and dynamic training progressions despite other improvements in function.
“It is a complex meniscal problem with acute and longstanding or chronic pathologies involved.
“Sam will be re-evaluated by club specialists over the next 48 hours and we will provide updates as to his management plan as the Club’s medical team works through all options available.”
A timeframe for Jacobs' return remains unknown.