Barcelona v Liverpool: Jordi Alba and Andy Robertson provide parallel threats from left-back

Sadio Mane measures 1.74m, so he’s no lighthouse in the penalty area. He can spring up high, though, and if a cross is perfectly calibrated, will pose quite a threat with his headers. The Senegalese scored two headed goals at the weekend, eased by some slack Huddersfield Town marking but mostly facilitated by the precision of Liverpool’s full-backs with their passes. Much of Liverpool’s resurgence, as Uefa Champions League contenders and relentless chasers of the Premier League title, has been propelled by those attacking full-backs, Trent Alexander-Arnold and Andy Robertson. Both are entitled to regard the broad canvas of Camp Nou, where they take on Barcelona on Wednesday night with a place in the European Cup final at stake, with relish. Lionel Messi stands four centimetres shorter than Mane. His heading technique is not bad either, though as he has the best feet in the game, he’s better served with crosses directed low. There not many who understand precisely to where as cannily as Jordi Alba, Barca’s livewire of a left-back. Seven of Messi’s goals in this La Liga-winning season have been set up directly by Alba, miniature allies on the same wavelength. The best left-back in the world? Alba is a candidate, Robertson not so far behind. Certainly both of them have had far better seasons than Real Madrid’s Marcelo, once the dashing, dynamic mould-breaker in a traditionally unglamorous position. Liverpool’s flying Scotsman and Barcelona’s Catalan express have common strengths: an eagerness to see and drive counter-attacks from deep in their own halves; the stamina to cover, over 90 minutes, the full length of their pitch. They are also footballers who, unlike, say, Liverpool born-and-raised Alexander-Arnold or Barcelona’s homegrown right-back Sergi Roberto, have come through bruising rejection to reach the top. Alba is a native of the Barcelona suburbs, and enrolled at the club’s feted academy as a kid. But he was not retained, informed, brutally, as he approached the age of 16, that his 1.70m height counted against him. Alba was then playing as a winger. The idea of offering his speed, and left-foot accuracy to another club as a full-back seemed unlikely: how, coaches would ask, could a man of his stature defend the back post? Alba bounced back, via lower-division football and a move to Valencia where he would be converted to full-back and mastered the role so impressively Spain had made him their first-choice by the European championships of 2012, where he scored in the final. Barcelona repatriated Alba that summer. He quickly made himself indispensable, as effervescent on his wing as Dani Alves had become as a right-back in the admired Barcelona of Pep Guardiola. Robertson, born in Glasgow, was also told he did not measure up, let go by Celtic at 15, told he was too small. In the same summer Alba was rejoining Barcelona, Robertson was preparing to sideline his football for a university degree when he was given an opportunity in the first-team at Queen’s Park of the Scottish third division. Via there, and then Dundee United and Hull City, he reached Liverpool in 2017. _____________________________ _____________________________ He was made Scotland captain at the beginning of this season, and last week named as one of three of the club's defenders - alongside Virgil Van Dijk and Alexander-Arnold - in the English Professional Footballers Association Team of the Year . “It has been fantastic to see him grow, develop and improve,” said Jurgen Klopp, the Liverpool manager, after Robertson in January extended his contract until 2024. You could almost hear purrs of approval from Liverpool’s strikers: eight of the goals scored this season by Mane, Mohamed Salah and Roberto Firmino have been directly supplied by the Scot. Those habits will shape one of Barca manager Ernest Valverde’s major selection decisions for Wednesday night. The task of patrolling Barcelona’s right flank shifts between Sergi Roberto and the Portuguese Nelson Semedo. Both are converted midfielders, although in Roberto’s case the midfield vocation remains a strong part of his portfolio and may advance his arguments as the best candidate, in the home leg, to restrict Robertson’s breaks. As for Alba, his tasks are many: to ensure his pace and experience act as Barca’s best backstop against the whiplash speed of Salah and Mane, while using his attacking nous up the flank manned by the relatively inexperienced Alexander-Arnold. If Alexander-Arnold looks back over his shoulder and sees Alba jetting clear, he knows enough to dread what often comes next: Messi ghosting across, confidently anticipating the perfect pass.

Barcelona v Liverpool: Jordi Alba and Andy Robertson provide parallel threats from left-back

Both players not only share similar traits, but have also taken similar paths to reach the top of European football

Liverpool train at Melwood before leaving for Barcelona