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Trent Alexander-Arnold said he underestimated Marcus Rashford when the pair went head-to-head against one another for the first time.

Playing on the left wing, Rashford scored both goals in a 2-1 win for Manchester United against Liverpool in March 2018, which Alexander-Arnold said was the most difficult experience of his career.

He told The Athletic's James Pearce (h/t Goal's Tom Webber):

"[That match against United was] the toughest in terms of a direct opponent and someone getting on top of me in professional football. I'd say I underestimated him.

"It was a massive learning curve for me. It was something that I hated happening. As a Liverpool player, it's probably the worst game of the season to perform like that. But when things like that happen you have to learn from them.

"It was a wake-up call. You hate days like that. You don't want to experience that. You remember how it felt and that makes you try everything you possibly can to ensure you don't have another one like it."

The game was Alexander-Arnold's 15th start in the Premier League.

He was taken off with 10 minutes of the match remaining, but Rashford had put the Red Devils 2-0 up by the 24th minute:

As Samuel Luckhurst of the Manchester Evening News observed, the right-back was left for dead by the striker:

It's perhaps a surprising admission that Alexander-Arnold underestimated Rashford, as the forward first broke into the United team back in the 2015-16 season, so he'd been a regular at Old Trafford for some time.

Rashford, who scored again when United faced Liverpool in October, turned 22 on Thursday.

The night before, he bagged two goals against Chelsea in a 2-1 Carabao Cup win that included this stunning free-kick:

It's safe to say Alexander-Arnold has recovered from his game to forget against his fellow England international, though.

The 21-year-old is a regular at Anfield now, and he played a key role in Liverpool racking up 97 points in the Premier League last season and winning the UEFA Champions League. He contributed a combined total of 16 assists across the two competitions.

This season, he's helped the Reds win nine of their first 10 matches in the league.

While he's occasionally targeted by opposition defences—as he was by United in the 2-1 win last year—he has developed into one of the best right-backs in the world.

He'll next come up against Rashford on January 19 when United visit Anfield. Rashford doesn't always play from the left, so they might not be in direct confrontation with one another, but if they are it will be fascinating to see how the two young players fare.