Nenad Bjelica was red-carded in the 74th minute for twice shoving Sané in the face after the winger demanded the ball from him to take a throw-in. The incident came as several Union players were indignant at having had a penalty appeal turned down shortly before.
“It is not to be tolerated, what I did,” Bjelica told German broadcaster Sky Sport. “Do I understand the red card? Obviously. I was somewhat excited because of the penalty episode that happened.”
Bjelica alleged that Sané had pushed him during the incident.
“He comes into my space to provoke me and obviously I don’t react as I should as a coach,” Bjelica said.
Bjelica could face a lengthy suspension. His team is next in action Sunday against fellow relegation candidate Darmstadt.
Bayern’s win leaves the German champion four points behind league leader Bayer Leverkusen.
Information from The Associated Press was used in this story.