The Red Devils have benefitted greatly through Paul Scholes' decision to return from retirement with the league leaders yet to drop a point whenever the midfielder has featured in the starting XI.
But with the 37-year-old nearing the end of his career, manager Sir Alex Ferguson has sought to bring in a creative attacking midfielder to replace Scholes within the next few seasons. The Daily Telegraph has now claimed that Gaitan is the player most likely to fit the bill with United ready to pay a reputed £20 million.
Inter Milan's Wesley Sneijder was considered to be an ideal replacement as he possesses the requisite vision, passing and scoring abilities that would allow Ferguson to employ an advanced playmaker capable of directing United's attacks but it has been difficult to prise the Dutchman away from the Italian club.
Lille midfielder Eden Hazard was another potential transfer target, with Ferguson making trips to France in order to scout the midfielder and evaluate his potential. However, with the likes of Tottenham and Arsenal also keeping a close watch, Ferguson would need to get involved in a bidding war in order to bring the midfielder across the English channel.
Gaitan, 24, is an Argentinean midfielder renowned for his dribbling abilities and he shares the lead in the Champions League assists chart with five assists to his name this season.
The two sides also faced one another in the Champions League group stage with the Portuguese side managing to eke out a draw on both occasions. Gaitan demonstrated a willingness to cut inside and test the goalkeeper, while also supplying a terrific cross from which Oscar Cardozo scored in the first match.
The Daily Telegraph reports that Benfica will get United defender Fabio for a season-long loan in return. Ferguson has already said that Fabio will go out on loan next season and although the Brazilian featured in United's Champions League final defeat to Barcelona last season, he has failed to progress as expected at Old Trafford.
Federico Macheda will also be used as a makeweight and be transferred to the Portuguese club. The young Italian striker is currently on loan at Queens Park Rangers and Danny Welbeck has already usurped him as Ferguson's preferred young striker at the club this season.
Ronaldo's agent, Jorge Mendes, is also said to be involved in the deal. Mendes was also responsible for helping bring Nani to United.
Manchester United currently lead the league and hold a five-point lead over city rivals Manchester City and are on course to win their 20th league title this season.