The Sporting Lisbon defender will arrive at Old Trafford having shone for Argentina at the World Cup, where he was named in FIFA's Team of the Tournament.
The 24-year-old will become the fourth of his countrymen to have turned out for United and here, Sports Mole has looked back on how the three previous Argentine footballers fared during their time at Old Trafford.
1. Juan Sebastian Veron (2001-2003)
Appearances: 82 Goals: 11
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Having arrived for a club-record fee of £28.1m in the summer of 2001, much was expected of Veron. After all, the 26-year-old had the reputation of being one of the world's best midfielders from his time in Serie A with Sampdoria, Parma and Lazio. The fact that he was sold to Chelsea just two years later for around half that price has resulted in many writing off his time with United as an expensive mistake.
While that viewpoint is understandable, Veron was a victim of having signed for the right club at the wrong time. He joined a side still basking in the glory of their Champions League and treble triumph of 1999 - a success that was achieved playing 4-4-2. In time, Sir Alex Ferguson would learn, with the help of his assistant Carlos Queiroz, that United's victory that season playing that particular strategy was the exception rather than the rule where European football was concerned.
Had a 26-year-old Veron been able to join United in 2007, we could have been talking about a much different spell for the midfielder. United were more methodical about their play, having abandoned the gung-ho style that had greeted Veron. He could have sat at the base of the midfield, picking out passes for the likes Wayne Rooney and Cristiano Ronaldo. That's not to say that there wasn't the odd bright point from his time at United, with particularly important goals being scored against Tottenham Hotspur and Arsenal.
2. Gabriel Heinze (2004-2007)
Appearances: 83 Goals: 4
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Regardless of how well Heinze performed throughout his three years at Old Trafford, he will never be looked upon fondly by the United faithful. Wanting to leave the club is one thing, but attempting to force through a move to bitter rivals Liverpool rendered all the committed displays that he put in meaningless.
The versatile defender arrived from Paris Saint-Germain for £6.9m and he quickly went on to establish himself in the left-back position. His tenacious style, which has drawn comparisons with Rojo, made him a firm favourite of the supporters, who would often be heard chanting 'Arg-en-tina' and actually voted Heinze their player of the season. Things would change, though, courtesy of a knee injury that he sustained in September 2005, which would sideline him for the remainder of the season.
During his absence, Ferguson signed full-back Patrice Evra and Nemanja Vidic and despite a rocky start to their United careers, by the time that Heinze had returned to fitness, they were established and his starting opportunities had been limited. It prompted the Argentine to push through a switch to Liverpool, but United dug their heels in and eventually sold him to Real Madrid for a reported £8m fee.
3. Carlos Tevez (2007-2009)
Appearances: 99 Goals: 34
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Putting the fact that he went on to join Manchester City aside, not signing Tevez on a permanent basis is regarded by some as one of Ferguson's biggest gaffes in the transfer market. For the same money that was used to purchase Dimitar Berbatov from Tottenham in the summer of 2008, Tevez's services could have been secured on a lengthy contract. Instead, the striker was made to play second fiddle to the Bulgarian, who failed to live up to the hype surrounding his £30m move, for most of the 2008-09 campaign.
After helping West Ham United to retain their Premier League status in dramatic circumstances with a goal on the final day of the season at Old Trafford, Tevez moved to the North-West on a two-year loan deal from the company that owned his rights - MSI. He'd go on to score 19 goals in all competitions as United won a Premier League and Champions League double, forming an exciting three-pronged attack with Rooney and Ronaldo in the process.
Largely confined to the bench following Berbatov's arrival, it was speculated that Tevez's relationship with Ferguson had soured during the following season. United are thought to have offered him a contract, but it didn't meet his demands, making him a free agent in the summer of 2009. His switch to City, for whom he ironically made his debut against United, made him public enemy number one as far as the red half of Manchester was concerned, but for two years, he, like Heinze, had been a favourite of the fans.