Muller scored only five goals last season, enduring a 999-minute league goal drought, and faces increased competition.
RB Leipzig are "lucky" they don't need to sell star midfielder Naby Keita, according to Liverpool manager Jurgen Klopp.
Borussia Dortmund have been fined and handed a suspended stadium ban because of fans' behaviour at the DFB-Pokal final.
Mexico striker Javier Hernandez has agreed to return to the Premier League with West Ham, the club confirmed on Thursday.
Franck Ribery says he was not "completely happy" with last season and has demanded more playing time at Bayern Munich in the 2017-18 campaign.
Borussia Dortmund captain Marcel Schmelzer has been ruled out for up to four weeks with a partial ligament tear in his right ankle.