Despite a shaky start, the Reds vice-captain had grown into the game, providing the assist for Diogo Jota's opener in the 31st minute with a fine corner.
However, with the score level at the break, Alexander-Arnold did not come back out onto the pitch for the restart, with Harvey Elliott instead coming on.
It was a change that ended up working wonders, with Elliott acting as an instant threat down the right-hand side, providing two assists in the second half to propel Liverpool to a 3-1 win.
That said, fans were unsure why the decision had been made to take Alexander-Arnold out of the game in the first place, with the Englishman so often pivotal to Liverpool's creative play.
The fact that creativity and attacking impetus had been noticeably lacking during the first half could explain his substitution as one with tactical reasoning - but there were definitely players having less of an impact on the contest then Alexander-Arnold, so why not bring them off?
This has brought some to speculate that Alexander-Arnold was substituted due to an injury scare - something that would act as a cause for concern due to the defender having only recently returned from the sidelines.
He told BBC Sport: "Same area in the knee. Nothing really bad but he felt it again and we have to see. We will assess it.
"We were made aware of it in the game so thought 'what can we do' then Trent said 'no it's fine'. But it's not as he feels it so we had to be careful and take him off."