The wait to find out who would replace Quique Setien at the helm of the Nou Camp didn't last too long as Ronald Koeman was announced as the next Barcelona manager.The Dutchman was a true Blaugrana legend as a player, having won honours aplenty and carving out his legacy in the iconic red and blue stripes and was part of Johan Cruyff's 'Dream Team'. Now, Koeman returns to the football cathedral to try and do so as a manager, and lead them back to their glory days.Barcelona, as things stand, are in need of a large squad revamp. The current squad of players is an amalgamation of various managers' choices and bad decisions in the transfer market. There are a lot of players who could be considered deadwood and need to be moved on and replaced with young blood with the future in mind.5 – @RonaldKoeman is the fifth Dutch manager at Barcelona; each of the previous four Dutch managers are in the top five most La Liga games for the club. Illustrious. pic.twitter.com/WTNWDAPaq0— OptaJohan (@OptaJohan) August 19, 2020The Catalans' president Josep Maria Bartomeu confirmed that the changes in the side are inevitable, saying;"I don’t to speak ill of anyone, I want to elevate the figure of these players, who have made the best club in the world. We have been winning trophies non-stop for 12 years. Now is the moment to start to say goodbye, with all the honours, to some of those players. The renewal of the squad will be as wide ranging as necessary so that the sporting project is a success."Koeman has overseen his fair share of quality signings at most clubs he's worked for, and has purchased some players who have gone on to do create distinct and commendable legacies for themselves.It is important to note that it would not be fair to give the Dutchman every ounce of credit for the transfers, given clubs' modern methods of scouting and identifying targets. Nonetheless, Koeman has been credited with some remarkable signings over the course of his managerial career.Here, we take a look at five of the new Barcelona manager's best signings.#5 Dusan Tadic | Southampton | €14mKoeman made Tadic his first-ever Premier League signingWhen Ronald Koeman moved to Southampton in 2014, the Dutchman used his Eredivisie links to purchase Dusan Tadic from FC Twente for a mere €14m. The Serb was a staple for the Saints both during and after Koeman's departure from Southampton.Tadic spent four years in the Premier League, a spell during which he scored 21 and assisted 30 goals. The 31-year-old moved back to the Eredivisie after his English endeavour when Ajax came calling for him. When he did eventually move, his career saw a turnaround of the highest order.38 - Dusan Tadic and Hakim Ziyech created more chances this Eredivisie season than any other player. Generous. pic.twitter.com/uGXASYgwuq— OptaJohan (@OptaJohan) October 7, 2019Tadic ripped apart defences at the tip of Ajax's attack as an unconventional forward and helped the Amsterdam club go until the semi-finals of the UCL in 2018/19. The former Saints man was absolutely lethal for his new club, and is likely to end his career playing for the Dutch champions. Koeman's first-ever Premier League signing proved to be an astute one.#4 Toby Alderweireld | Southampton | LoanAlderweireld spent one year on loan at SouthamptonAnother signing with a connection to Koeman's former club Ajax, Toby Alderweireld was a player the Dutchman signed on loan while he was at Southampton. The then-unexperienced centre-half was brought in as part of Koeman's revamp of Southampton after agreeing a deal with an option to purchase with Atletico Madrid.After a stellar season in the Premier League, Southampton wanted to complete an outright purchase of the Belgian. However, that wasn't possible as Atleti then sold Alderweireld to Tottenham Hotspur who offered more than double of what the Saints did to purchase him. Despite Southampton threatening to take legal action against Atleti, Spurs completed the signing.1 - Toby Alderweireld is the first player to score a goal and an own goal in the first half of a PL match since Fabian Delph for Aston Villa vs West Brom in January 2014; Delph's instance was also at Villa Park, while his own goal was also scored in the 9th minute. Oddity. pic.twitter.com/HXVkIE4LjN— OptaJoe (@OptaJoe) February 16, 2020Alderweireld went on to become one of the most experienced defensive stalwarts in the Premier League and is currently one of Spurs' most senior players. On his day, he is one of the best ball-playing defenders in the top-flight. The Belgian is just one short of playing his 150th league game for the North London club.Also read: 5 Worst signings made by Barcelona under Josep Maria Bartomeu