Ilkay Gundogan has said he believes referees "could have sent off more players" for bad challenges in matches against Manchester City.
City manager Pep Guardiola urged officials to do more to protect his players after a number of strong challenges, adding that it would be "impossible" to win a quadruple because of injuries.
Late last month, City winger Leroy Sane was hurt in a late challenge from Cardiff defender Joe Bennett in an FA Cup tie and faces a spell on the sidelines.
City players including Bernardo Silva have called for more protection and, speaking to German publication Sport Bild, Gundogan said: "Maybe it's because of our performances this season, maybe it's just our subjective perception.
"In the end, in football there is one man on the pitch who is judging all of this.
"I believe they [referees] could have sent off more players in recent matches, but it did not happen.
"We do not complain but put up with it, even though it is bitter that injuries like Leroy Sane's result from it."
Gundogan, 27, also addressed the transfer saga of former Borussia Dortmund teammate Pierre-Emerick Aubameyang, who joined Arsenal last month.
Gabon international Aubameyang was criticised for his conduct and failed to attend an important team meeting in the run-up to his move and Gundogan, who left in 2016 with a year remaining on his contract, said: "I don't know if I could have pulled it through like Auba did it.
"I was also criticised at BVB for wanting out, and I could partially understand the fans' reaction. But I only wanted to be honest and always gave everything for the club."