Liverpool center-back Virgil van Dijk has named Paris Saint-Germain forward Lionel Messi as the toughest opponent he has faced in his career so far.Speaking to Sky Sports, the Dutchman recollected how difficult it was to face Messi and Barcelona in the first leg of the 2018-19 UEFA Champions League semi-final. He said:"I would say Lionel Messi. He's still the best football player in the world. Him and Cristiano Ronaldo have been doing unreal numbers for the last decade, and it's incredible what they have achieved. I would say Messi [is the toughest opponent] because it was a very tough evening in Barcelona when we lost 3-0. Luckily, we turned it around at Anfield."Lionel Messi was the star when Barcelona defeated Liverpool 3-0 in the first leg of the semi-final during the 2018-19 Champions League. The Argentine netted a sensational 30-yard free-kick that ended up being one of the best goals scored that season.However, Liverpool managed to pull off one of the most incredible comebacks in the second leg of the tie, beating the Catalan giants 4-0. The Reds went on to win the Champions League that season, which was Jurgen Klopp's first trophy as manager of the club. Everything Messi@EverythingLM1O🎥 | Virgil Van Dijk: “I think Leo Messi is still best football player in the world.” Class recognizes class. 🙌8:48 AM · Oct 4, 202157098🎥 | Virgil Van Dijk: “I think Leo Messi is still best football player in the world.” Class recognizes class. 🙌 https://t.co/fGHLqqOXzOVirgil van Dijk heaps praise on Bundesliga star Erling HaalandVirgil van Dijk also praised Borussia Dortmund star Erling Haaland, stating that he admires the Norwegian's strength and pace. He has compared the forward to Leicester City's Jamie Vardy.The Liverpool star said:"Haaland is also a special striker: he’s strong, he’s quick and he’s got all the attributes to make a defender’s life very, very difficult. The first time [playing against him] was when he came on at Anfield and scored for Salzburg. He was very quick, aggressive, very direct. It's a bit like how Jamie Vardy plays, but Haaland is maybe a little bit stronger than Vardy."Anfield Watch@AnfieldWatchVirgil van Dijk on Erling Haaland:“Haaland is a special striker, he’s strong, he’s quick. He’s got all the attributes to make a defender’s life very, very difficult. The first time was when he was at Salzburg he scored at Anfield. He was very quick, direct.” #awlive [mirror]12:11 PM · Oct 4, 202192346Virgil van Dijk on Erling Haaland:“Haaland is a special striker, he’s strong, he’s quick. He’s got all the attributes to make a defender’s life very, very difficult. The first time was when he was at Salzburg he scored at Anfield. He was very quick, direct.” #awlive [mirror] https://t.co/ZAva5iZ4lFVirgil van Dijk's return from injury has been a massive boost for Liverpool. The defender missed the majority of last season after sustaining an ACL injury against Everton in the Merseyside derby.Liverpool had a disappointing title defense last season as most of their first-team center-backs were on the sidelines. The Reds have addressed those issues in the summer transfer window when they spent £36 million on RB Leipzig defender Ibrahima Konate.Since his comeback, Virgil van Dijk has featured in all of Liverpool's Premier League games so far this season. The Reds currently find themselves in second place in the table, one point behind league leaders Chelsea.