The Reds began with an early goal from Mohamed Salah, but the game soon devolved into a methodical, physical contest as the visitors fought back.
Sadio Mane doubled the lead in the second half, only for Callum Paterson to stab home an opportunistic effort and cast doubt over the result.
“We could have done better, that’s how it is, but we played on Wednesday, we played today, and we had to create and create and create,” he told reporters.
“That’s really hard work, to be honest, and it makes it so difficult. For your most creative football you need fresh legs and fresh players.
“You cannot change the full team, because you need rhythm as well.”
The manager also praised Cardiff’s efforts, saying “I have a lot of respect for what Cardiff are doing, but it’s not so easy to play against!”
And after Shaqiri’s first goal for the club in another impressive cameo display, Klopp added that “bringing on that quality is a massive difference.”