Manchester United's fixture against Queens Park Rangers this Sunday afternoon takes on an unusually high level of importance given just how difficult Louis van Gaal's side have found the start of the 2014-15 campaign, with the Dutchman's team yet to record a victory.However, United return from the international break buoyed by the return of several injured players, with midfielder Ander Herrera's comeback detailed byThe Guardian's Jamie Jackson,in addition to the three new signings who are expected to pull on the red of Manchester United for the first time on Sunday.Daley Blind, Marcos Rojo and Radamel Falcao are all in line to make their respective debuts for United this weekend, with all three players having the potential to turn United's stuttering start to the season around.With Blind and Falcao having both officially arrived on transfer deadline day, this is the first opportunity for the pair to play. However, in the case of Rojo there has been a lengthy battle with theUK Border Agency, as per Anthony Hay of the Daily Mail, regarding the former Sporting Lisbon defender's visa, which was resolved on September 4th, a full fortnight after the Argentine's arrival at Old Trafford.There have been a myriad of issues which have caused United difficulty this season, with the most noticeable being thetroubles the defence hasendured inswitching to a 3-5-2 system.At times United's defenders have looked uncomfortable on the ball with there being so much space in front of them, but as the risk of leaving a gap behind them by marauding forward has simply been too high, players have been unwilling to venture forward and quicken the tempo of the team's play.The lack of bite and defensive awareness in the middle of midfield has also been a problem. Whilst this is not a new concern, with United having failed to suitably replace Owen Hargreaves since his departure in 2011, the defence has not received much protection from midfield.Blind is the player to provide that aforementioned protection. Having enjoyedhis best season to date as a defensive midfielder with Ajax last term, as recognised by the Dutch FA who handed Blindthe Golden Shoe, as per the Daily Mail's Jack Gaughan,the tough tackling nature of Blind's game is something that will slot seamlessly into United's midfield.Marouane Fellaini was expected to be the signing to provide this last season, but the Belgian has not been able to find his feet at Old Trafford thus far, mainly due to a lack of technical ability needed to link all aspects of midfield play at a club with the philosophy of Manchester United.Blind has the perfect balance of defensive ruggedness and technical ability, ensuring that the Dutchman will be able to contribute effectively to both phases of United's football.The added protection given by Blind will aid the three-man defensive line should Van Gaal stick with the 3-5-2 system, while his defensive midfield presence will also provide a degree of attacking freedom for the two central midfielders alongside him.In either a 3-5-2 or a 4-3-3, Rojo will add something unique to United's defensive options. The Argentinian has yet to feature for United, but his energy and enthusiasm for defending is something the club has lacked so far this season.WhileRojo is not the most orthodox defender, a prime example of thisbeing his 'Rabona' clearance inside his own penalty area during the World Cup, there is animpressive innate defensive ability there as well as natural speed.United have lacked energy in defence this season which has impacted play in two ways.Firstly, players have been lacking in both confidence and energyand thushave been unwilling to get forward when the space opens up. With Rojo and Blind in tow, there will be situations where Rojo goes forward, as Rio Ferdinand used to do, while Blind will fill into the gap left behind, ensuring United are not leftisolated at the back.Secondly, the lack of speed in United's back three this term has seen opposition teams get significant joy from runs in behind catching a defender either in possession orflat footed. Rojo has the speed to be able to cover these situations with Van Gaal having been suitably impressed by the defender during the World Cup, even going as far to say he was "enchanted" by the 24-year-old, according to FourFourTwo.I played him in the World Cupagainst Argentina,so Ihadto analyse Argentina.[From] that video Iwas already enchantedabout himbecause my philosophyis you have to buy players who fit in the profile, and Ithink Marcos fits in the profile as a left central defender but also as a left wing back.He played a fantastic World Cup, so I am very pleased.Finally, Falcao, the forward who took all the headlines on deadline day with his loan move to United, as detailed by Mark Ogden of The Telegraph, is expected to make his first appearance for Manchester United against QPR this Sunday. While supporters have expressed angst at losing a fan favourite and academy graduate in Danny Welbeck to make way for the Colombian, there is no doubting the 28-year-old's goalscoring prowess, whichismost welcomeat a time when United's forward line have not been close to firing on all cylinders.Robin van Persie is still a way off full fitness, whileWayne Rooney is not as prolific as he has been in years gone byalthough the latter was United's top scorer in the Premier League last term with 17 goals, according to statistics provided by WhoScored.com. This is not good enough for a team that harbours ambitions of at least a top four finish.Falcao will bring goals to the team, despite having only just returned to action following an Anterior Cruciate Ligament injury suffered last season. United need to return to the top four and to do that you need goals, on a regular basis. Throughout his career, Falcao has scored goals wherever he has gone and there is little evidence to suggest that won't be the case at Old Trafford. Of course it remains to be seen the long-term impact his injury will have on him, however, in terms of a physical presence, Falcao fits the build necessary to bully defenders. There is little excuse for United's poor start to the campaign, but it must be noted that the upcoming meeting with Harry Redknapp's QPR is the first occasion where you can say United are heading into a match at full strength. The match is a must win for the Red Devils, despite the season being just four matches old, with the competitiveness of the Premier League dictating that teams who have ambitions for a top four finish must be consistently successful throughout the campaign. With the exciting list of debutants expected at Old Trafford on Sunday, United have the perfect opportunity to record a win and totally transform the mood around the club as the quest for a top four finish begins in earnest. Read more World Football news on BleacherReport.com Click here to read full news..