Center-backs form the heart of the defensive lines in football. They are usually the strongest players on the pitch but their role also requires them to be good at reading the game.As football has evolved over the years, so has the role of central defenders in the game. Managers nowadays encourage their central defenders to be their first source of attack. Long balls into the final third or a splitting pass into midfield are a part of many teams' strategy.Sky Sports Premier League@SkySportsPLAntonio Rudiger is reportedly set to become one of football's highest-paid defenders, potentially earning up to £400,000 a week if he leaves Chelsea as a free agent next summer.8:15 AM · Dec 10, 20219732635Antonio Rudiger is reportedly set to become one of football's highest-paid defenders, potentially earning up to £400,000 a week if he leaves Chelsea as a free agent next summer.Ball-playing center-backs in high demand at the momentCenter-backs that are good with the ball add another dynamic to the game. A lot of teams prefer to build their game from the back nowadays. Hence, having an accurate passer of the ball in the defensive third helps out here.It is no wonder that central defenders post some of the highest pass conversion rates across Europe's top five leagues at the moment. Subtle tackles, interceptions and clearances made by these players are easy to overlook in a fast-paced game.Defenders usually taking a back seat in the age of attacking football. However, here we take a look at the five most underrated center-backs of the 21st century.#5 Joel MatipJoel Matip has been a utility player at LiverpoolLiverpool have one of the best center-backs in the world in their ranks in Virgil van Dijk. But we are not talking about the Dutch defender here. Joel Matip, a player Jurgen Klopp signed for free in 2016 from Schalke 04 has enjoyed a good run with the Reds.Football on BT Sport@btsportfootballJust Joel Matip being Joel Matip Jordan Henderson's face says it all... #UCL3:59 AM · Feb 17, 20227057892Just Joel Matip being Joel Matip 😅Jordan Henderson's face says it all... #UCL https://t.co/9NvR6SdUlnThe German-born Cameroonian began his career with Schalke winning the DFB Pokal and the DFL Supercup with the club in 2011. His aerial prowess also made him a good threat from set-pieces as he scored three goals in five of his seven seasons with his boyhood club.While he might've struggled to start regularly in the Premier League for Liverpool, he has paired up well with Van Dijk in recent seasons. He provides a good option from the bench for squad rotation and has delivered top-notch performances whenever called upon by Klopp.#4 Ivan CordobaIvan Cordoba is an Inter Milan legendIvan Cordoba was one of the finest defenders in South America during the first decade of the 21st century. The Colombian center-back joined Inter Milan in the summer of 2000 from San Lorenzo and spent 12 seasons with the Serie A giants.While he did not feature regularly during the 2009-10 campaign, he still managed to be a part of the team that won the continetal treble that season.He scored his final goal for the Colombian national team in the final of the Copa America 2001 against Mexico. Alongside Marco Materazzi, he formed one of the best central defensive partnerships in Italy in the first decade of the century.