Mats Hummels was surprised by the reaction from Borussia Dortmund supporters to his transfer to fierce rivals Bayen Munich during the close-season.
Hummels became the latest Dortmund player to move to the Allianz Arena for a deal reported to be in the excess of EUR30million, following in the footsteps of Robert Lewandowski and Mario Gotze.
The defender - who originally moved from Bayern to Dortmund in 2008 - was criticised by some fans for re-joining the German champions, something he finds hard to understand given his eight-year stay at the club.
"It has quickly been made out to be ingratitude, but then what does gratitude mean?" Hummels told Kicker.
"Does gratitude mean that you have to spend your whole life with this one club? I feel I have always been fully and absolutely loyal to my club.
"I have been a little bit surprised by the magnitude of the reaction. I thought people already knew about the bond I had with Munich.
"I've been spending my time in Munich in each of the last summer and winter breaks. It's quite strange that I of all people am being accused of trampling over the values of club loyalty."
Hummels made his Bayern debut in their DFL-Supercup win over Dortmund and played in the DFB-Pokal victory over Carl Zeiss Jena.
He could make his Bundesliga bow for the club on Friday against Werder Bremen.