Carlo Ancelotti says Bayern Munich will play it safe with goalkeeper Manuel Neuer and have him sit the season opener.
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.