When Liverpool and Real Madrid meet in the Champions League Round of 16 first leg, it will be the latest instalment in a rivalry between two clubs who have frequently boasted World Cup and Ballon d'Or winners within their ranks.
Some of their stars have made their way between the Santiago Bernabeu and Anfield directly, while others have played for both heavyweights after turning out for other clubs in between.
The Sporting News takes a look at some of the names to have appeared in both of the famous shirts.
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Nuri Sahin
Turkey midfielder Surin was 23 and the Bundesliga Player of the Season when he joined Real Madrid in 2011, signing for Jose Mourinho in a transfer that failed to live up to his promise as one of Europe's hottest prospects.
Twelve was the unlucky number for Surin, who was restricted to 12 appearances in Madrid because of injuries and only played 12 times during a five-month loan at Liverpool the following season. He had another happy spell at Dortmund between 2014 and 2018 and is currently the manager of Turkish Super Lig side Antalyaspor.
Fernando Morientes
Targetman Morientes won La Liga twice and the Champions League three times during an extravagantly successful spell with Madrid between 1997 and 2005.
After averaging more than a goal every three games for his former club, Morientes managed less than one in five for Liverpool, where he won the FA Cup and Super Cup but was cup-tied for the Reds' Champions League triumph shortly after he joined them.
The 2003/04 Champions League top scorer returned to Spain with Valencia in 2006 and moved to Marseille in 2009, retiring the following year.
Fabinho
Brazil midfielder Fabinho could be seen as a player Madrid let escape their grasp, having somewhat mysteriously played for the club's reserves and made a sole senior appearance during a loan move from Portuguese side Rio Ave during the 2012/13 season.
Five years at Monaco — the first two on loan — culminated in Fabinho catching the eye of Klopp, who signed him in 2018 for around £39 million ($47.5 million).
Fabinho completed his move little more than a month after Liverpool lost the 2018 Champions League final 3-1 to Madrid, but he has since won every trophy going with the Reds, including the Champions League in 2019.
He battled back from injury to start last season's final, which ended in a 1-0 win for Madrid over Klopp's side.
Michael Owen
The sixth-highest goalscorer of all time for England looked every inch a future Three Lions legend when he scored on his debut for Liverpool as a 17-year-old in 2017.
Owen beat Real Madrid hero Raul to the Ballon d'Or in 2001, by which time he had announced himself on the international scene in spectacular fashion.
Perhaps Owen was not helped by having to contest a starting berth with the likes of Raul and Ronaldo after he joined Real Madrid in 2004, leaving a season later with a respectable record — for a player predominantly used as a substitute — of 16 goals in 46 appearances.
👟 At the age of 19, Michael Owen had already won the Premier League Golden Boot twice.
— Football Tweet ⚽ (@Football__Tweet) October 5, 2021
⚽ He was Liverpool's top goalscorer between 1997 and 2004.
🏅 In 2001, he won the Ballon d'Or.
🤕 Imagine how good his career would have been without recurring injuries. pic.twitter.com/zsPTO080up
Although he was yet to hit peak age for most strikers, Owen was a faded force by then, his fall from his formidable best as swift as his ascent to the hall of fame had been.
Owen went on to have unspectacular spells at Newcastle United, Manchester United — with whom he won the only league title of his career, in 2011 — and Stoke City.
Steve McManaman
Owen was perhaps hoping to emulate the success of former team-mate Steve McManaman's path from Merseyside to Madrid.
The tricky winger had been a key figure in Liverpool's success between 1990 and 1999 and one of the best widemen of the early Premier League years, tempting Madrid to swoop when he could not agree a new contract.
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The move paid off handsomely for the man whose solitary FA Cup and EFL Cup wins had seemed scant return for his often-thrilling performances in a red shirt.
McManaman won the Champions League twice between 1999 and 2002, La Liga in 2001 and 2003 and the Supercopa de Espana and UEFA Super Cup.
He joined Manchester City between 2003 and 2005 and can now occasionally be seen alongside Owen in their roles as television pundits.
Antonio Nunez
While it would be an exaggeration to describe Nunez as a one-season wonder for either club, the right-winger spent the 2003/04 campaign as a peripheral figure for Madrid before joining Liverpool as part of the deal involving Owen ahead of the start of the following season.
Nunez's one season at Liverpool saw him win the Champions League as a semi-regular and become the only player for the club whose only goal came in a cup final.
That was a 113th-minute consolation as Liverpool lost the EFL Cup final 3-2 to Chelsea. He's now retired after spells in Cyprus and Spain.
Alvaro Arbeloa
Dependable full-back Arbeloa emerged from Madrid's youth ranks and would become a firm favourite at the Spanish giants and Liverpool via a season with Deportivo La Coruna.
Compatriot Rafael Benitez took Arbeloa to Liverpool in 2007, where he would become a Champions League and Premier League runner-up either side of winning Euro 2008 with Spain.
The £5 million ($6.1 million) deal that took him back to Madrid in 2009 would be an astonishing bargain these days, and his return was rewarded with two Champions League titles, La Liga, a Super Cup and the Club World Cup before a Premier League swansong with West Ham in the 2016/17 season.
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Nicolas Anelka
Exceptional on his day and infuriating when off the boil, Anelka was a burning young talent at Arsenal when Real Madrid signed him for around £22 million ($28 million) in 1999.
The move proved to be the first stumbling block of a nomadic career, and Anelka returned to PSG a season later after failing to settle at the Bernabeu.
Nicolas Anelka Liverpool goals #ClassicLiverpoolGoals pic.twitter.com/Xbe5Rn2S0H
— Classic Liverpool Goals (@goals_lfc) October 25, 2018
The France forward joined Liverpool on loan for the second half of the 2001/02 season, but his return of five goals in 20 appearances was insufficient to persuade Gerard Houllier to extend his interest.
Liverpool's current Premier League title arch-rivals, Manchester City, signed Anelka in 2002, where he was prolific. His most successful seasons in terms of trophies, though, came at Chelsea between 2008 and 2012, when he won the Premier League once and the FA Cup twice.
Xabi Alonso
Liverpool fans were devastated when stylish midfielder Alonso, who scored the equaliser in their thrilling Champions League final win over AC Milan, left for Real Madrid for £30 million ($36.5 million) in 2009.
Spain midfielder Alonso also remains beloved at Madrid, helping them to La Liga and the 2013/14 Champions League title, among a haul of trophies.
Alonso's movement and visionary passing abilities made it little wonder when Pep Guardiola moved in 2014 to sign him for Bayern Munich, where he won the Bundesliga in each of his three seasons with the club. He has since coached for Madrid at youth level and is now head coach of Bundesliga side Bayer Leverkusen.
Jerzy Dudek
As endings to a successful career go, joining Real Madrid for four years as a back-up to legendary goalkeeper Iker Casillas isn't a bad way to sign off.
That's how Poland goalkeeper Jerzy Dudek spent the final stretch of his playing days, between 2007 and 2011, following a far more eventful six years with Liverpool.
Signed from Dutch giants Feyenoord, Dudek won the FA Cup and EFL Cup at Liverpool but will perhaps most cherish his heroic role in the 2005 Champions League final.
Milan's Andriy Shevchenko was perhaps the most feared forward in Europe at the time, and Dudek thwarted the Ukraine hotshot with a magnificent save with the score at 3-3, as well as denying him from the spot and keeping out Andrea Pirlo's penalty in the shootout.
The two-time Dutch Goalkeeper of the Year is one of the few players to have won more trophies with Liverpool than they did with Real Madrid.
