Diego was furious that Bastian Schweinsteiger was not dismissed after the two players clashed in Bayern Munich's win over Wolfsburg.
Die Roten secured victory through Thomas Muller's second-half strike but the Bavarians were perhaps fortunate to have still had 11 men on the field at that point given Schweinsteiger shoved Diego in the back of the head 26 minutes in.
The Brazilian expressed his incredulity at the fact referee Bastian Dankert chose only to give a yellow card for the incident, with the VfL players demanding a more robust punishment.
"He hit me in the back of the head," Diego was quoted by Bild after the game.
"I felt a contact in my neck. That was surprising to me, I did not see him coming.
"I think everyone has seen the situation. Everyone should judge what they've seen. It is sometimes difficult to understand how referees think. I will try to accept that."
Bayern edged a tight game to keep themselves level on points with Borussia Dortmund at the top of the table, but Schweinsteiger's former team-mate, Ivica Olic, insisted that a red card could have swung the game in favour of the visitors from Lower Saxony.
"I have now seen the scene again on television," the 34-year-old Croatian said.
"Schweinsteiger only gets a yellow, but for me it's red. He hit him, and the ball was nowhere near. If Diego had done that, it would have been red. It was a defining moment in the game."
The victory moves Bayern to 19 points from seven games, second only to Dortmund on goal difference, while Wolfsburg fall to ninth.