The right-back has been in magnificent recent form and looks back to his best.
However, Jurgen Klopp's men are going to have to manage without one of their talismans for an extended period of time.
How long will Alexander-Arnold be out for?
Liverpool assistant manager Pep Ljinders confirmed ahead of the Fulham match that Alexander-Arnold had suffered a knee injury during the 2-0 win over Arsenal in the FA Cup.
The Reds are already without Joel Matip, Andrew Robertson and Kostas Tsimikas, while Virgil van Dijk was ill at the weekend.
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So, an injury to Alexander-Arnold is the last thing they needed.
However, it appears as if the defender will be out for three weeks, meaning he should be back for Liverpool's trip to the Emirates at the start of February.
Speaking about the injury, Ljinders said: "Trent hyperextended his knee, so he has a little tear in the lateral ligament of his knee.
"He had a scan. He will be out for probably three weeks. It's a big blow. We will really miss him.
"We will have to find new dynamics without him because he made our game flexible. Even in bad spells, he was the one putting the balls where we needed the difference.
"He will get some rest, and then hopefully, he can come back to where he was. Because this guy was decisive in all the games and was the one who created constantly for us from deep."