The England international, 20, is making a name for himself as a deadly executor of set pieces.
And he caught the eye again on Saturday as the Reds eased to a 3-0 win over the Hornets to keep pace with Premier League leaders Manchester City.
Alexander-Arnold gave Ben Foster no chance with a fine effort to put his side two up in the second half after Mohamed Salah's opener, before Roberto Firmino rounded off the rout.
Indeed, one former Premier League star sees parallels with an England star of yesteryear.
"He has everything," ex-Tottenham and Newcastle star David Ginola said to Sky Sports.
"He's a fast thinker. I like players who take a risk when they do things.
"Every time he has the ball he's going to create something, something will happen. He has talent, pure talent.
"[That is] one of the greatest positions, David Beckham had that great position when he was kicking the ball. The balance is absolutely fantastic."
Liverpool old boy Jamie Carragher and manager Jurgen Klopp were also bowled away by the youngster's prowess, with Carragher saluting his "courage" at stepping up while sharing the pitch with Salah.
And Klopp added after Saturday's match: “Trent’s free-kick… wow! It was time actually. It was long ago that we played Hoffenheim!"
Liverpool will be back in action on Wednesday, where Paris Saint-Germain await in Parc des Princes.
The Merseyside team currently level on points with Napoli atop Group C, but with PSG just one back there is no room for error for any team in the last two matches of the first round.
Even fourth-placed Red Star Belgrade can still muscle their way into the knockout stages with a strong finish, having picked up four points from as many games so far to sit just two behind the leaders.