Moreno was in tears as he was helped down the tunnel shortly before half-time at Anfield, with James Milner replacing him on the way to a remarkable victory.
The Spaniard had been in excellent form before his injury, though Milner provided an able deputy, laying on three goals in the second half in the Champions League.
Klopp has made no secret of his desire to retain Moreno has his first-choice left-back this season, with Milner returning to a regular midfield berth after a season in the role in 2016/17.
And the German tried to remain optimistic when discussing the prospect of a long-term injury for Moreno after the game.
“We came to a little shadow of the night that Alberto needed to get substituted,” he told reporters.
“It was a strange situation. He’s a tough guy: if he cannot continue the game then we should consider it could be something serious.
“In the treatment room he was a little bit more positive, so maybe we are lucky and it’s not too serious. We will see.
“Because we need all the boys for the next few weeks, but especially this week, for the game on Sunday.”
“I can imagine tomorrow, somebody will make a story [about] Jordan Henderson, the captain, was not involved,” he continued.
“I have to make hard decisions and tonight it was like this; Hendo will play the next game, 100 percent, and he could have started tonight but we had to make a decision.”
Extolling the virtues of his new-found squad depth, Klopp also highlighted the selection problem he would still face if Moreno was sidelined.
“If Alberto is out for a few games—I don’t know—then of course we have Robbo and we have Milly,” he added.
“That’s all good, but we need all the players, we need freshness.”