BVB went into Saturday’s match on the back of an impressive 8-4 victory over Legia Warsaw in the Champions League on Tuesday, but they were unable to replicate that performance at the Commerzbank-Arena.
Dortmund are now nine points behind surprise leader RB Leipzig in the Bundesliga standings, with their away form causing particular concern, as they have now lost three league matches away from Signal Iduna Park this season.
Tuchel concedes his side's away form must improve sooner rather than later, while also lamenting their overall performance during the defeat to Frankfurt.
"You cannot win any away games in the Bundesliga with such glaring deficits in your game," Tuchel told reporters.
"There were technical flaws, tactical flaws and mental flaws. We lacked desire. Our performance was one big flaw. It already started on the training pitch this week."
The 43-year-old has been frustrated by Dortmund's season as a whole, labelling their inconsistencies over the opening months of the campaign as "frustrating".
He added: "Our entire season so far is one of highs and lows, which is very frustrating."