Now here’s a question the answer to which may surprise you.
It was, of course, the 4-3 win in the Europa League quarter-final second leg back on April 14 2016, a night that arguably kickstarted the Jurgen Klopp era.
Less obvious, though, is that as many as seven of those who began for the Reds that evening could play a part again this forthcoming campaign.
However, closer inspection of those names highlights how Liverpool have been gradually upgraded and evolved in the intervening years.
Throughout the team, players have been brought in to further develop the starting line-up, an improvement on what went before, with those being replaced in turn often becoming valuable and required alternatives.
Indeed, only one of those seven starters began the Champions League final win over Tottenham Hotspur in Madrid last month. Five were on the bench.
Back on that famous Anfield night, Simon Mignolet was in goal, now an experienced deputy to Alisson Becker.
At right-back, Nathaniel Clyne has been usurped by Trent Alexander-Arnold. On the opposite flank, the departed Alberto Moreno by Andy Robertson.
It’s a similar story at centre-back, with Mamadou Sakho sold and Dejan Lovren, scorer of the dramatic winner, now behind Virgil van Dijk, Joel Matip and Joe Gomez in the pecking order.
In midfield, Emre Can has long gone to Juventus and both Adam Lallana and the evergreen James Milner have, at least with view to the long term, been surpassed by Jordan Henderson – injured for the game three years ago – Gini Wijnaldum, Fabinho and Naby Keita.
In attack, only Roberto Firmino of today’s celebrated front three was at the club, although he was joined by Divock Origi. Philippe Coutinho, the other starter that evening, is now elsewhere.
Most of the departures have come on the bench, with Danny Ward, Brad Smith, Martin Skrtel, Lucas Leiva, Joe Allen and Daniel Sturridge gone, while Sheyi Ojo is now on loan at Rangers.
For Origi, Friday’s friendly will have a certain poignancy, a reminder of the circuitous route he has travelled to get back into a similar position.
Back then, Origi had jumped above Sturridge in the pecking order, scoring in both legs against Dortmund and in impressive form before suffering a serious ankle injury against Everton.
His subsequent travails are well documented, culminating in his remarkable contribution in the latter stages of last season’s triumphant Champions League run and the signing of a new contract.
Origi’s renaissance was the ultimate example of how Klopp remains loyal to those he believes can still do a job.
Recalling the last starting line-up against Dortmund is further evidence of that.