Striker Raul Bobadilla has rejoined Borussia Monchengladbach on a two-year contract after passing a medical.
Fabian, 28, was initially set for a two-month spell on the sidelines while undergoing treatment for lower back problems.
Dembele, 20, a target for Barcelona, went on strike last week and was suspended by Dortmund after missing training without permission.
Twelve-year-old attacker Youssoufa Moukoko scored another brace in his second appearance for Borussia Dortmund's under-17 side.
Bayern Munich aren't what they used to be, but then again, neither is the Bundesliga. Raf Honigstein previews the season.