Thus far, any one of Carrick, RVP or Rafael would be worthy winners. De Gea and Evans have been unsung heroes too.
Carrick's importance is perhaps best emphasised by his absence than his actual presence on the pitch; without him we lack composure and structure in midfield, and we lose a string-puller capable of penetrative passing too, as demonstrated by his magnificent assist against Chelsea.
It's fairly simple why Van Persie is in contention; not only is he second top scorer in the league but many of those goals have been decisive, such as his hattrick at St Mary's. He's performed in many of the big games too, scoring at Chelsea, Man City of course and both games against Liverpool. All in all he's added not only plenty of goals, but a commendable assist maker and architect of goals too, he's been an inspiration.
Rafael has been one of the most improved players and has developed into one of the world's top full backs. His attacking ability was never in question, but his defensive side and composure were sometimes found wanting on occasion, yet this season he's nullified the likes of Ronaldo, Bale and Hazard and is now a guaranteed starter on the teamsheet and that is a testament to the progression he's made.
De Gea hasn't got the credit he deserves from anyone apart from united fans themselves, and even some of them have been over-critical. At the beginning of the season himself and Lindegaard were frequently battling for the number one spot and the young Spaniard raises his game to condemn the more than capable Dane to the bench. Even in his Atletico days he caught the eye with spectacular shot-stopping, but that has improved further still since moving to OT. There have been a deceptively large amount of matches in which he's saved our skin; his heroics at Stamford Bridge earned a brilliant three points, he made some remarkable saves in the derby against City, he thwarted Fulham several times too, with a double save at OT and the fingertip save at Craven Cottage to deny Ruiz particularly memorable. He was fantastic at White Hart Lane too, only late lethargy from the defence preventing the perfect performance. Then we get to his Bernabeu heroics; he was tremendous, the save from Coentrao in the early stages defies all manners of description, how he managed to see through the traffic and divert a well-struck shot onto the inside of the post. Magnificent.
Evans has been a brilliant stalwart and unquestionably has been our best defender for the past two seasons now. He's often been renowned for his ice-cool composure that is reminiscent of Ferdinand, but this season has really worked on his tackling and has become one of the league's best defenders and one of the most underrated players around. His performance for Northern Ireland against Portugal in Lisbon was one of the greatest individual performances I can recall seeing, and his club exploits make him a more than worthy candidate.
Im genuinely struggling to pick a winner from these 5, but I think Van Persie just nicks it purely on the impact he's had, transforming a team that ultimately went trophy-less to one that was challenging on three fronts in March, and arguably still should be.