The Reds' ambitions for a quadruple ended at Holmes Park after Ryan Hardie’s second-half penalty sealed a major upset.
Missing key players like Mohamed Salah and Virgil van Dijk, Arne Slot’s team couldn’t force extra time, leaving Fowler to question their response after falling behind.
Post-game, Fowler said: "Not great, if I'm being honest. The response (was) probably in the final five minutes of the 90 and then the nine minutes.
"We saw the Liverpool that we probably wanted to see earlier in the game, where the intensity was better, they were moving the ball quicker and they were getting the ball into the box. That was missing for 85 minutes.
"You come into an atmosphere like this, it was intimidating, Liverpool players are used to playing in them atmospheres. But the intensity in which they moved the ball during the game, up until 85, was very un-Liverpool.
"We give them so much praise in midweek but it was the polar opposite tonight."