To say Manchester United have had a European nightmare this season would be an understatement.
Eliminated from the Champions League in the group stages and subsequently knocked out of the Europa League in the Round of 16—all less than a year after an appearance in the Champions League Final.
While Premier League glory remains a very real possibility, it is difficult to hide from the disappointment of Europe. It was always destined to be a rebuilding year, having lost so many veterans and replacing them with such promising youth.
Now that those young players have faced the harsh reality of European competition, they will come back with the experience necessary to mount a better challenge for the Champions League, but the squad could still benefit from a few key signings.
Each of these five players addresses a key issue or concern in the current squad and would almost undoubtedly improve upon the talented squad Sir Alex already has at his disposal.
It is highly unlikely, if not impossible, that United will sign all five of these players. The financial outlay required would be enormous and unrealistic. At the other end of the spectrum, it is also entirely possible that none of these five will arrive at Old Trafford in the summer.
Regardless of who actually arrives, any combination of these five players would go a long way in preparing United for a run at European glory in the 2012-13 season.
Leighton Baines is the man to replace Patrice Evra at left-back for Manchester United if that is deemed necessary in the summer.
Evra has increasingly become a liability over the past two seasons, and the left side of the United defense appears quite vulnerable. Baines would be an excellent option to challenge Evra for the left-back berth and potentially even replace the Frenchman.
Baines has arguably been the best and most consistent left-back in the Premier League for the past two seasons, proving impressive in defensive duties and an important attacking threat for Everton. He could provide a similar threat going forward that Evra currently does, while also proving more reliable in defensive responsibilities.
He is also an excellent option at set pieces, which is another area in which United could use a boost of quality. Baines is now 27 years old and in the peak years of his career. One issue last summer was signing too many young players to replace key veterans.
Although Baines lacks significant European experience, he comes proven with plenty of Premier League experience and could make a quick transition to European competition.
Baines is a key player for Everton, and the club are unlikely to part with him easily. His current deal expires in June 2015, which gives Everton significant bargaining power for one of the best left-backs in the Premier League.
United should still be able to secure a transfer for a reasonable fee to address a key issue in the squad.
Javi Martínez was one of Athletic Bilbao's star performers during their Europa League triumph against Manchester United, and it very possible he will have caught the attention of Sir Alex Ferguson.
If you can't beat them, have them join you.
Martínez impressed in both legs at centre-back, although that is not his natural position. Not that anyone would've noticed, given he looked natural in defense. The Spaniard is a centre-midfielder by trade, and his versatility to play both as a defender and holding midfielder could prove a valuable asset to United.
The midfield has been a major concern over the past few seasons, and Martínez is certainly an intriguing option to address the issue. A holding midfielder with some fantastic passing ability and a superb comfort in possession, Martínez could bring some much-needed defensive quality to the midfield, while also contributing to create attacking opportunities.
Given some of United's defensive injury concerns over the past few seasons, Martínez could also fill in as a centre-back if needed. The defense has been stretched thin at times this season and such a versatile player would be greatly appreciated.
Some media sources have suggested Martínez could cost as much as £33 million this summer, with Manchester City and Liverpool also interested. A move could be hard to secure, but as one of the most promising midfielders in Europe it could prove worthwhile.
Finding long-term heirs to Paul Scholes and Ryan Giggs was never going to be cheap. If the club are willing to finance the transfer, Martínez could be the way forward in Europe.
Manchester United are still missing a genuine midfield enforcer and France's Yann M'Vila may be the perfect candidate to fill the void.
M'Vila is only 21 years old, but has already made 18 appearances for the France national team and captained his club side Rennes. He is also praised by many as one of the most promising young defensive midfielders in the game.
The defensive midfielder is a vital role in European competitions. Roy Keane bossed the United midfield for many years and was key to their run to the Champions League Final in 1999. Owen Hargreaves was eventually brought in to fill that role following Keane's departure, and he proved a valuable asset in the 2008 Champions League triumph before falling victim to injury.
The role remains unfilled since Hargreaves' injury and his consequential departure from Old Trafford. To compete against the likes of Barcelona, such a player is necessary. In the final last season, Michael Carrick played as the holding midfielder, but he is hardly a true defensive midfielder.
M'Vila would be an excellent player to fill the role, if not the ideal solution. With an impressive physicality, M'Vila can impose himself on the midfield, dominating his opposition by using his strength. He is excellent at tackling and hard going into challenges. Such grit is valuable in the midfield.
Although his primary attributes are defensive, he is also an excellent passer and could prove valuable in starting an attack.
Rennes manager Frederic Antonetti already confirmed that M'Vila would be leaving the club this summer, although United have not yet been linked with a move for the midfielder. It would be worthwhile for the club to start making inquires before missing out on one of the most promising young midfielders in the game.
Already proven both in Ligue 1 and the France national team, he possesses some important experience to provide a valuable asset in the Champions League.
The defensive midfield position is vital for European competition, and M'Vila is one of the best to address that concern.
Eden Hazard is strongly linked with a move to Manchester United after reports that Sir Alex Ferguson scouted the Lille playmaker last week.
The Belgian international may well prove to be the long-term option for the United midfield. Ryan Giggs and Paul Scholes will not be around forever, and Hazard would be an excellent option to prepare for the day when the duo inevitably call it quits.
While a holding midfielder is likely more necessary, a creative presence could prove valuable as well. Tom Cleverley has plenty of potential to prove an attacking threat long-term, but may not yet be ready to be a key player for United in the Champions League.
United often struggled to create quality goal-scoring opportunities this season in Europe, almost as much as they struggled to keep clean sheets. Just an extra bit of attacking flair in the side could be what is needed to unlock defenses.
One of the best options to provide that flair is Hazard.
Hazard would arrive having already made 25 appearances in European competition for Lille. One of the most sought-after young talents, Hazard is a proven attacking threat, capable of playing as a winger or an attacking midfielder.
As such an exciting talent, it is unsurprising that he is also attracting attention from Manchester City. It seems likely he will be on the move this summer with big clubs interested, and Hazard acknowledges that being looked at by Sir Alex is a very exciting prospect.
Hazard may cost as much as £25 million, perhaps even more, but his quality could be exactly what United is missing to take the club back to the quality they demonstrated in Europe over the past few seasons.
Manchester United could be in the market for a striker in the summer with Dimitar Berbatov and Michael Owen likely to depart, and Fernando Llorente may be the perfect solution to add depth in attack.
While the club will likely retain Wayne Rooney, Danny Welbeck and Javier Hernandez, a fourth striker will be needed to give adequate attention to both the Premier League and Champions League, in addition to the FA Cup and Carling Cup.
Like Martínez, Llorente demonstrated against United in the Europa League that he could prove a valuable addition at Old Trafford. His goal in the second leg was fantastic, and with experience for Athletic Bilbao in Europe and as a member of the Spain national team, he could be a ready-made addition to challenge in Europe.
With two fairly young strikers in Welbeck and Hernandez, Llorente would offer valuable experience and maturity in attack at the age of 27. Typically, Sir Alex Ferguson seems to prefer younger player who are still fulfilling their potential, but losing two experienced strikers may require a slightly older option in this scenario.
Llorente is unlikely to come cheap, like the other signings mentioned here, but he is another that at least deserves some attention from the scouts at United. Losing a striker of Berbatov's quality and experience is a blow to the depth at United, and his spot should be filled. Llorente could likely be more involved than the Bulgarian and perhaps push for an even larger role.
Scoring goals has been a struggle at times in Europe this season, and the added threat of a proven striker could be an immense boost to United's chances in the Champions League next season.