Wayne Rooney and five other players Manchester United need to sell this summer

Old Trafford appears to be littered with deadwood

One of Alex Ferguson's greatest managerial skills was knowing when to sell a player. The former Manchester United manager got rid of stars who appeared to be in their prime on numerous occasions and very rarely did the transaction come back to bite him. In 1995, Paul Ince, Andrei Kanchelskis and Mark Hughes were sold, much to dismay of football pundits and United fans alike. However, the departed stars failed to again reach the heights they'd reached at Old Trafford, and Ferguson replaced them with the fabled Class of '92. Ruud van Nistelrooy was sold to Real Madrid in 2006, United went on to win more Premier League titles in the three years after his departure than during his five years with the club. Ferguson jettisoned David Beckham in 2003, replacing him with Cristiano Ronaldo, and cut his losses with Juan Sebastian Veron the same year. The only blot appears to the sale of Jaap Stam in 2001, otherwise Ferguson was a master in knowing when a player had peaked. It'd be interesting to hear the Scot's view on the current United squad. We've looked at six players Ferguson may have let leave were he still the United manager. Some players may seem more than capable of still performing, but could be about to enter a downturn in their careers. While others have just reached the end of the line at Old Trafford. Robin van Persie Robin van Persie's impact during his debut season was akin to that of Eric Cantona or Ruud van Nistelrooy in their first years at Old Trafford. The Dutchman was incredible, the key variable in the destination of the Premier League title. Van Persie joined in August 2012 after a stunning season with Arsenal, where he scored 37 goals in 48 appearances, and continued his form at Old Trafford. United won their record 20th league title as Van Persie scored 30 goals in 48 appearances, including goals against the team's main rivals Chelsea, Manchester City and Arsenal. The striker embedded so well at Old Trafford it was though he was destined to be a United legend. Less than two years later, Van Persie is in decline. It could be argued no-one fared worse, other than David Moyes, from Alex Ferguson's departure. Van Persie has been a shadow of his former self since the Scot left and his compatriot Louis van Gaal has yet to help fully revive the striker's once deadly form. Van Persie has scored eight goals in 17 games this season, and has, at times, shown flashes of brilliance. The striker had two chances away to Southampton, and finished them both. However, Van Persie is less mobile than in his prime, has become peripheral in games and will be 32 in the summer. The creative spark he once had seems to have been extinguished as he's had just five assists in the past two seasons, compared to 19 in the previous two. Van Persie's role now is to only score goals, but if he's not getting chances, he's not involved in the game. If the club are to ever challenge for titles, and compete in Europe again, they need a more dynamic forward leading the line. Chris Smalling Manchester United's defence this season has been makeshift to say the least, and needs obvious strengthening, whether this month or in the summer. However, the mere fact Chris Smalling, Phil Jones and Jonny Evans have failed to make the position their own doesn't bode well for their futures. The trio have been hampered by injuries and the constant reshuffling of the defence, but Smalling could become the fall guy for the team's defensive woes. The England defender is arguably the lesser of the three. Not quite as good on the ball as Evans, and not quite as good at the dirty work as Jones. It could even be the scenario that all three depart this summer, with each player's contract up for renegotiation and no sign of new deals being signed. One could make a case for United getting rid of them all, but Smalling may be first to go. The defender has seemingly failed to deliver on his potential and would find his game time limited should the club sign the much needed top class player in the position. Radamel Falcao While he technically won't be sold, as the player is on loan, United will save a fortune by not making Radamel Falcao's deal permanent. Amazingly a 28-year-old centre forward, returning from his second anterior cruciate ligament injury and after moving to a new country, has failed to shine. Who would've guessed it? Not Ed Woodward anyway. United's executive vice-chairman sanctioned the season long loan from Monaco, costing the club £16 million, with another fortune to be paid to make it permanent in the summer. Falcao has scored three goals in 11 games, playing 634 minutes and has been hampered by injuries. The striker has cost United £5.3 million per goal so far. Falcao wasn't even on the bench for the team's last game, the 1-0 loss at home to Southampton. Van Gaal said he opted to select 19-year-old James Wilson instead, citing the youngster's pace as the reason. A damning verdict on Falcao, who was once the most feared centre forward in the game. The Colombian may hit those heights again, but it looks unlikely to be at Old Trafford. Rafael A ever-present in Ferguson's final years, Rafael does not seem part of Van Gaal's long-term plans. The right-back was fit for the game against Liverpool, but the manager chose to omit him from the squad, saying he only selects players on 'merit'. With moves for Seamus Coleman and Southampton's Nathaniel Clyne mooted, both obvious upgrades on the Brazilian, Rafael's days at United appear numbered. Darren Fletcher Darren Fletcher has only featured 12 times for United this season, an achievement considering his past troubles with a chronic bowel condition, but limited compared to the game time he received prior to his illness. Fletcher, unfortunately, doesn't seem capable anymore of playing in central midfield for an elite team. Since breaking into the first-team in 2003, the midfielder has made 342 appearances for United and was a influential player in past United title successes. But, with his contract due to expire in the summer, the 30-year-old looks to be in his final months. Louis Van Gaal may even let him go this month. Wayne Rooney A controversial choice, but hear us out. Wayne Rooney has had a very productive season so far, playing in numerous positions, the United captain has scored eight goals and registered four assists in 17 games. One could even argue that, besides goalkeeper David de Gea, Rooney has been United's best player. However, for how long can he continue? And in what position? There's an argument to be made that Rooney, at this current moment, is in a similar stage as Van Nistelrooy in 2006 or Beckham three years previous. A standout player, but his best days have passed. Rooney has played eight of his 17 games this season in central midfield, and has been very effective in the role against lesser sides, such as Newcastle United at home, where he scored twice. However, the recent game against Southampton highlighted his flaws in the position. Rooney struggled against the Saint's compact midfield and was forced deep to receive the ball. The United captain mainly plays a series of diagonal balls to the wide players when he features in central midfield. A tactic that will work against the Premier League also-rans, but not one capable of breaking down a well-drilled side such as Southampton. It's difficult to see Rooney excelling in the role as he gets older, games become faster and defences become tighter. Van Gaal is a big fan of Dutch midfielder Kevin Strootman, Michael Carrick is still very important and Ander Herrera has shown flashes of promise. Where will Rooney fit in? The United manager has been reluctant to play him centre forward, a strange decision considering United play two strikers in most games, and Rooney has not become the No 10 many believed he would. Before Rooney enters Steven Gerrard territory, where fans and pundits call for his inclusion in any position possible and he has to be shoe-horned into the team, it may be best for United to jettison the player. It's unlikely to happen, as he's the club's captain, highest paid player and has had his best season since 2011/12. However, Rooney is also a streaky player. Look back at his career and it's apparent one good season tends to be followed by a poor campaign. Rooney will be 30 this year. He's not old by any means, but he's possibly the oldest 30-year-old in the Premier League. The Liverpudlian has been playing first-team football since 2002, that's an awful lot of football, particularly for an attacking player of Rooney's physique. While it may seem strange to say so now, United could be best departing with the player who may soon break the club's scoring record.