When Baier was tackled near the RB Leipzig bench late in Augsburg's 1-0 victory during Tuesday's bad-tempered match, the 33-year-old spat in the direction of RB coach Ralph Hasenhuettl.
The television camera caught Baier also making an obscene gesture.
The DFB confirmed Wednesday they will investigate, referee Daniel Siebert not having seen the incident.
Baier twice tried to apologise, both after the final whistle on the pitch and again in the dressing room, but Hasenhuettl rejected the apology.
"What should I apologise for?" he told Sky.
"My god, it's a football match and emotions are involved.
"I made a gesture, what more can I say?"
However, Baier apologised in a statement posted on social media channel Instagram on Wednesday.
"Out of the emotion, I let myself be swept into making a gesture that I don't know how I got to," Baier wrote.
"I apologise to all those who interpreted it as offensive.
"I apologised to the team before training, because the senseless gesture pushed our great performance into the background.
On Wednesday, Hasenhuettl said he was 'done' with the subject, but tensions clearly remain.
"I told him after the game what I thought of it and I was not going to accept an apology in that moment," said Hasenhuettl.
"With all the emotion, and I've seen more emotion in games where more has been going on, I have never seen something like that.
"I promise one thing: should one of our players pull a similar stunt, he will certainly hear something other than an accusation against the opposing coach," he added, referring to Baier's comment about the rejected apology.
Augsburg are having a stellar start to the season with 10 points from their first five league games to go third in Germany's top flight.
In contrast, Champions League side RB Leipzig are struggling to recapture last season's form, which saw them finish second to reigning champions Bayern Munich.
They are eighth having lost twice in the league so far this season after starting the 2016/17 campaign with a record 13-game unbeaten run on their Bundesliga debut.
Disclaimer: No Business Standard Journalist was involved in creation of this content
You’ve reached your limit of {{free_limit}} free articles this month.
Subscribe now for unlimited access.
Already subscribed? Log in
Subscribe to read the full story →
Smart Quarterly
₹900
3 Months
₹300/Month
Smart Essential
₹2,700
1 Year
₹225/Month
Super Saver
₹3,900
2 Years
₹162/Month
Renews automatically, cancel anytime
Here’s what’s included in our digital subscription plans
Exclusive premium stories online
Over 30 premium stories daily, handpicked by our editors


Complimentary Access to The New York Times
News, Games, Cooking, Audio, Wirecutter & The Athletic
Business Standard Epaper
Digital replica of our daily newspaper — with options to read, save, and share


Curated Newsletters
Insights on markets, finance, politics, tech, and more delivered to your inbox
Market Analysis & Investment Insights
In-depth market analysis & insights with access to The Smart Investor


Archives
Repository of articles and publications dating back to 1997
Ad-free Reading
Uninterrupted reading experience with no advertisements


Seamless Access Across All Devices
Access Business Standard across devices — mobile, tablet, or PC, via web or app
