Federico Chiesa’s sucker-punch strike just 11 seconds into the second half floored the Champions League holders in Turin.
Chelsea slipped to a second straight 1-0 loss, following Saturday’s Premier League defeat by Manchester City.
Caught napping for the goal with collective minds clearly still ruminating on half-time team talks, Chelsea were punished by Juve’s superior sharpness.
Lamenting the manner of the goal, Tuchel said: “It should be impossible to concede an easy goal like this at this level in the first seconds of the second half.
“You know what’s coming, you have defensive organisation like we have, so normally at all times it should be possible to defend it.
“And we got punished for it, of course.”