Trent Alexander-Arnold says a clash against Manchester United two years ago was "the most difficult game" he has had to date, as Liverpool prepare to face their arch-rivals once again.
When Liverpool made the trip to Old Trafford in the 2017/18 season, it proved to be an unhappy affair for the visitors as they were beaten 2-1 in the Premier League.
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On that mid-March afternoon, Alexander-Arnold was tasked with marking his England team-mate Marcus Rashford, who scored twice in the first half to send United on their way to victory - and it is not a game the Liverpool right-back has forgotten in a hurry.
Speaking exclusively to Sky Sports' Patrick Davison, he recalled: "That was the most difficult game I've had in my career so far. It was probably a lesson I needed to learn because I used it in the right way and didn't dwell on it too much.
"I used it as motivation to make sure something like that doesn't happen again, or you try your best to do that.
"That game made me a better player. It was that feeling on the pitch of letting the team and the fans down because it was my direct opponent that scored two goals and they were probably my fault, especially the first one.
"You try your hardest not to feel like that but with the way football is, and the human brain works like that, if you do make a mistake then you blame yourself and beat yourself up.
"I've tried to make sure that doesn't happen again because that feeling wasn't nice at all."
There are huge questions marks over Rashford's fitness for the Renault Super Sunday clash this weekend, but Alexander-Arnold does not believe it will alter Liverpool's game plan too drastically.
"Whether he plays or not, there will be a world-class player there [in Rashford's position], no matter what," he said.
"There might be a change of style in terms of the player but nonetheless, it will be a player of high quality and you know it's going to be a difficult game. It won't really bother us, but you understand his quality and the form he's in is fantastic.
"Going into the game, you've got to be ready for who you're coming up against and know what they're about. In the 1-1 draw earlier in the season, he [Rashford] bagged a goal so we'll be hoping that it doesn't happen again and try and work on things like that during training."
'The rivalry is always there'
Alexander-Arnold came through the Liverpool academy and is well versed in the meaning of the rivalry with United, but he refuses to label his team as the favourites ahead of the weekend.
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"I probably heard about Man Utd about the same time as I did Liverpool," the defender reflected. "Wayne Rooney moving to Man Utd was massive at the time and the special players they had then were amazing. Then Cristiano Ronaldo came and was doing crazy things, the sort of things people maybe we hadn't seen in the Premier League before.
"They were winning so many league titles, it was hard to ignore, so you knew they were a good side. Growing up, you then start to learn what their past was like and Liverpool's, and you realise they are fairly similar in terms of the trophies that they've won, the history that they've got, and the rivalry that was there.
"Growing up, they [Liverpool vs Man Utd matches] were amazing games that I'd always try to watch and were probably the biggest games of the season for Liverpool at the time. I remember the 4-1 at Old Trafford in 2008/9 as clear as day, with the grey kit. I loved that kit!
"I always remember Fernando Torres doing special things against United at that time in his career. I remember Steven Gerrard doing a lot and the team at the time was amazing. They were pushing for the league title that season as well, so it was a time to be excited as a Liverpool fan.
"They [United] carried on going, we probably slowed down a little bit, but the history and the rivalry was always there. You knew that from a young age that they're the two most meaningful wins of the season - the fixtures fans will look at before a ball is kicked is Everton and Man United.
"For the fans, it means a lot to beat them, but we need to not get caught up in our emotions and let it ride over into the game. It's a big game, the atmosphere will be amazing, but we've got a job to do. We need the fans to be there, to get our tactics right and make sure we're not going in there with complacency because of our league position.
"We know we're there for a reason and that's our mentality, and the way we approach games has been good so far - but we've still got a long way to go and that's the way that we look at it.
"Are we favourites? I don't know. Maybe if you go on betting websites then we are, but you can't take that for granted. There are favourites in every game and the favourite doesn't always win. We know that because we probably haven't been favourites in a few games and won, and vice versa, so anything can happen in the Premier League.
"It's about the respect that we've got for them. Obviously you can't pay too much attention because you've got to go and do a job on them, but we understand their strengths and every team has weaknesses. It's about exploiting them and understanding what they've got to hurt us and so far, they're the only team to have taken points off us.
"We know they're a difficult side to play against and we got the late equaliser at Old Trafford [in October] so it's going to be a very tough game. We know what we're coming up against and they've got a team of very good players.
"We're in a good position right now but we can't take that for granted. We know they will come to Anfield looking to take points off us again and we need to stop that from happening."
Friends reunited?
There will be a few familiar faces on the opposing team, with Alexander-Arnold playing alongside some United players for England. However, national-team ties will be put to one side on Sunday.
He said: "I know the English lads - Harry Maguire, Marcus [Rashford], Jesse [Lingard], Luke Shaw and Aaron Wan-Bissaka were involved in an England squad earlier on in the season.
"I don't know if you can say 'friends' because we don't socialise outside football, but I wouldn't say I socialise with anyone from any other team really. There are different fixtures, different days of playing, and either you or them have a game nearly every day so you don't have too much time to do that.
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"You're focused on yourself and your own team. It's the modern-day football where it is like that but when you're meeting up at England, the club rivalry goes away. However, when you're at your club, you can't think about being friends at England because come Sunday, we're facing each other and we need to beat them and that's the mentality.
"I'm one of them in the tunnel where I don't want to be having hugs and wishing them the best. You have to shake hands before the game and that's mutual respect between two players, but we are trying to take points off each other and there's a game to win."
Follow Liverpool vs Man Utd across Sky Sports
Liverpool vs Manchester United is live on Super Sunday from 4pm; kick-off 4.30pm. Sky Sports customers can watch in-game clips in the live match blog on the Sky Sports website and app. Highlights will also be published on the Sky Sports digital platforms and the Sky Sports Football YouTube channel shortly after the final whistle.