Full-backs, once the least fashionable role on the field, didn't garner many headlines in the past, but in modern-day football, they've become a vital component in various playing-formations.In the current climate, full-backs are required to play a pivotal role at both ends of the pitch, and hence many sides have invested heavily in strengthening this position in recent transfer windows. That has led to some interesting full-back pairings being assembled.On that note, let us have a look at the five best full-back pairings in European club football at the moment:Five best active full-back pairings in Europe#5 Daniel Carvajal and Ferland Mendy (Real Madrid)Dani Carvajal (left) and Ferland Mendy (right) could form a deadly full-back combination in the future.Real Madrid returned to the pinnacle of Spanish football last season by clinching their first La Liga title in three years. And even though their full-backs Daniel Carvajal and Ferland Mendy weren't exactly the talismanic figures during the campaign, they certainly played their parts.Carvajal, who labelled himself a 'fail' after Real Madrid's catastrophic 2018-19 season, redeemed himself with a series of assured performances last season. He made six top-flight assists, the second-highest in the division by a defender, and scored once but truly stood out for his defensive contributions.The Spaniard's positional awareness ensured that the chances created by the opposition team from his flank were minimal while his timely tackles, 3.6 per game, proved to be a thorn for attackers.75% - @realmadriden's @LaLigaEN win percentage without Daniel Carvajal since he joined the club in 2013/2014 season, compared to 65,1% with him. Absence#RealMadrid #LaLigaSantander pic.twitter.com/Kopaihc2L9— OptaJose (@OptaJose) January 26, 2020On the opposite flank, Mendy also made a compelling case for himself. He often rotated the left-back spot with Marcelo but showed signs of promise, dribbling his way forward to create scoring opportunities while also making vital interceptions.#4 Robin Gosens and Hans Hateboer (Atalanta)Robin Gosens (left) and Hans Hateboer (right) have had a huge impact in Atalanta's free-scoring football.Atalanta were one of the sides to watch last season for their swashbuckling brand of football that not only produced goals at a phenomenal rate but helped the team finish in the Serie A's top-three. Last season, the Bergamo-based outfit reached the quarterfinals in their first-ever appearance in the Champions League.An important factor behind Atalanta's prolific performances up front was their full-back pairing of Robin Gosens and Hans Hateboer. The duo made overloads in the attack to destabilise opposition defenses and let their forwards create various combinations.The pair were also highly productive in terms of direct goal-contributions. Gosens in particular emerged as the Serie A's most dangerous full-back with nine goals and eight assists while his Dutch counterpart registered six assists in all competitions and also scored twice in the Champions League.8 - Robin #Gosens has scored eight #SerieA goals this season (all from open play); the last defender to have scored more (excl. penalties) in the competition was Christian Maggio in the 2007/08 campaign (nine). Weapon.#AtalantaLazio— OptaPaolo (@OptaPaolo) June 24, 2020