Nicolas Anelka has announced on his Twitter account that he is to leave West Brom with immediate effect.
Mauricio Pochettino expects to be at Southampton next season and is looking forward to working with chairman Ralph Krueger.
Hummels has long been linked with Spanish giants Real Madrid and Barcelona, but the 25-year-old is happy at the Signal-Iduna-Park.
The former Bayern Munich stopper admits that he is not driven by winning lots of trophies.
"I do not necessarily need to play for the best team in the world to remain in a situation to have a certain chance to grab trophies. That's a fact," he told Die Welt.
"I am a player of Borussia Dortmund and, so to say, I would prefer one UEFA Champions League title with Borussia Dortmund over six with an other club."