Sir Alex Ferguson's Top 5 Biggest Heartaches as Manchester United Manager

Even with 12 EPL titles under his belt, Manchester United manager Sir Alex Ferguson still craves success in the worst way.

He knows, however, that domestic glory won't come easy, with many talented teams throughout the league and flaws even in his own squad. 

The following factors (ranked according to how much they affect the team) serve as heartaches to Sir Alex, keeping him up at night and ultimately making him worry about his team's future success.

(All stats and info via ESPN FC.)

5. Manchester City

Despite a disappointing season to date and a 15-point gap to make up, Manchester City are still a dangerous team. 

With the likes of Joe Hart, Sergio Aguero and Yaya Touré, United's crosstown rivals have the pieces to be a title contender for years to come.

However, due to only meeting United twice a year in EPL action and the Reds having little reason to worry about them right now (they hold a comfortable first-place lead), they cannot be ranked any higher on this list.

With less underachieving, and more consistency, City would really worry Sir Alex.

4. Nani

One of the most enigmatic players on the planet, Nani has the pure talent to take over a game.

But only if he wants to.

The Portuguese attacker can be extremely dangerous at his best, blowing by defenders with tricky footwork, whipping in pinpoint crosses and producing goals of sheer brilliance.

Without commitment and effort, however, Nani's signature dribbling skills become useless maneuvers that don't help the team at all.

Instead, it becomes clear that Nani's primary goal is to impress the crowd instead of helping his team score.

Every player has the occasional bad game, but Nani's are caused by a lack of interest and effort—not talent—that is sure to frustrate Sir Alex.

3. Spreading Playing Time of Attackers

Often described as a "good" problem, depth is an extremely valuable asset over the course of the season.

It gives managers bundles of flexibility, allowing them to seamlessly craft lineups around player form and recent injuries.

However, that depth must be managed meticulously, as limited playing time for a certain player can make them feel unappreciated, lower their morale and ultimately end up with them requesting a transfer.

Aside from the EPL's second-leading scorer Robin van Persie, none of the other forwards on Manchester United have made a significant case to be a surefire starter.

Danny Welbeck has been maddeningly inconsistent, sometimes failing to get involved at all and other times producing moments like this.

Javier Hernandez has been a super sub—eight goals but nothing more—as he's failed to produce consistently as a starter in league play.

Lastly, Wayne Rooney hasn't been scoring as much, instead embracing his playmaker role, with nine assists thus far. However, Rooney still has 12 goals—a respectable total—and if anyone on this slide deserves a permanent spot in the lineup, it's him.

With such an abundance of forwards, Sir Alex Ferguson puts his team in a position to win, but risks losing one if he does not keep their playing times at an equilibrium.

2. The Back Line

Although their back line has improved dramatically as of late, it is probable that United's early-season defensive woes still linger in the mind of their manager.

Through their first 19 games, the Reds conceded a total of 28 goals, allowing the likes of Reading and Newcastle to notch three goals apiece. Though they suffered from injuries, it was obvious that United's defense wasn't playing up to potential, with their poor marking and sluggishness forcing their attackers to bail them out.

The last 10 games have been much better, with Sir Alex's squad allowing only three goals and racking up seven clean sheets.

To be crowned EPL champions, Sir Alex will continue to focus on defense, as he won't soon forget last April's breakdown vs. Everton that ultimately cost them the title.

1. Wayne Rooney Transfer Saga

Although he's not having a great season by his standards, Wayne Rooney is by no means having a disappointing one.

With 12 goals and nine assists, the Englishman has scored at a decent rate, while showcasing his ability as a passer and defender in his role directly behind the striker. 

Despite only a slight drop off in his production, Rooney's role on United has diminished, with Shinji Kagawa and Ryan Giggs taking away some of his playing time. Perhaps the best proof of his sudden fall from grace at United was Sir Alex's benching of him in their second leg Champions League match vs. Real Madrid. They went on to lose that game 2-1.

Although Sir Alex may no longer think Rooney is one of the world's best players, there are plenty of other teams ready and willing to take him off his hands.

According to The Guardian, Rooney could be headed to Bayern Munich or Barcelona, while The Mirror reports that Monaco could make a "mega bid" for him.

Whether or not Rooney leaves this summer, Sir Alex will be wondering if he truly did disrespect the 27-year-old and what it will take for him to keep him in red.