Hummels has become a big part of the Bayern Munichs squad, but this was not always the case.
Mats Hummels
Bayern announce Mats Hummels deal
Hummels had been heavily linked to Bayern, and will now join Renato Sanches
Mats Hummels likely to join Bayern Munich
Borussia Dortmund chief executive Hans-Joachim Watzke expects Dormund defender Mats Hummels to join Bayern Munich