Thomas Tuchel called out Dayot Upamecano for giving away the penalty that saw Lazio claim their first-leg round of 16 win against Bayern Munich on Wednesday night.
The Bundesliga champions were looking to bounce back quickly from their difficult weekend tie against league leaders Bayer Leverkusen, but found themselves unable to push past their hosts in Rome.
After failing to convert a number of strong first-half chances courtesy of Harry Kane and Jamal Musiala, Bayern Munich's fortunes went from bad to worse after the break.
A hefty challenge from the France international on Lazio's forward Gustav Isaksen not only saw a penalty handed to their opponents, but Bayern go down to 10 men after Upamecano was given a straight red card.
Ciro Immobile was able to smoothly convert the penalty and send Lazio through to the second-leg at the Allianz next month with a slender lead.
After the final whistle, the former Chelsea manager stressed that he was 'frustrated' with the result, and his player's actions - but reserved criticism for the whole team performance itself.
'We're frustrated and angry about the defeat,' Tuchel said. 'I think we lost the game, I'm not sure Lazio won it.
'We did everything we could to fall behind, making errors and losing confidence. (There was) no need for Upamecano to go in like that. It's not wild or intentional - but just block the shot.'
As the clock ran down, Bayern Munich looked increasingly impatient hunting for an equaliser, but it was Isaksen who had arguably the strongest chance after the penalty and Lazio were unlucky not to go 2-0 up.
Tuchel said that the defeat was 'completely our responsibility', citing early chances from his side that went untaken.
'We started well, had a chance in the first minute
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