Long known as an ineffective squad player for the Red Devils, Chris Smalling could reinvent himself as a vital cog in United's team this season under Van Gaal.

At the very least, he will surely get more opportunities, as Rio Ferdinand has joined QPR and Nemanja Vidic has taken his talents to Inter Milan. The loss of two experienced center-backs should see Smalling's tally of 21 starts from last year rise.

He could certainly benefit from United's switch to a 3-5-2, which the Englishman thinks could bring out his attacking attributes, according to the club's official website:

I probably like this system more than the traditional 4-4-2 because it gives us a lot of freedom to play and be aggressive. As a defender I’d like to think that’s my game.

Smalling, a player who has often looked raw thus far in his career, can showcase his composure on the ball and physical prowess in Van Gaal's three-man defense.

While Chris Smalling's role at his position is likely to change this season, Wayne Rooney's position is likely to change altogether.

With his new Dutch manager switching to a two-striker formation, he will be able to play in his natural position alongside Robin van Persie while Juan Mata slots into his favored No. 10 role as well.

Though Rooney's efforts last season cannot be classified as disappointing—he averaged one goal or assist per game—his sometimes lackluster play and inability to be involved made United fans question if he was still one of the greatest players on Earth.

His numbers (17 goals, 10 assists) are impressive, but Rooney wasn't always playing top-notch football. He went from December to February without scoring at one point, struggling to find the net against Cardiff City, Stoke City and Fulham.

However, Rooney was still one of United's best players in an absolute disaster of a season, and his form should only improve now that he'll be in a formation where he can consistently play alongside Van Persie and Mata. 

With an impressive preseason and United's recent announcement that he'll be captain for the upcoming season, the stage is set for Rooney to have one of his best years yet.

After a devastating 18-month period stricken by injury, per The Telegraph, Darren Fletcher is finally having some things go his way. 

According to the club's official website, Fletcher will be United's vice-captain this season.

Hours before that announcement, he scored his first goal in nearly two years in a 2-1 win vs. Valencia.

Fletcher's smart and composed play has seen him combine well with newbie Ander Herrera, and he is looking like an impressive player once again.

With Michael Carrick out for 10 weeks, per the Daily Mail, Fletcher can make the role of holding midfielder his own with strong play to open the season. 

Since winning the 2011-12 Players' Player of the Year at United and being handed the No. 7 shirt, Antonio Valencia's career has plateaued. He's been unable to play solid football on a consistent basis.

A talented player, Valencia is something of a tweener. He is perhaps more defensively stout than the average winger, but he is also less technically gifted than such a winger. However, his game-breaking speed has often been too much for his managers to pass up, typically being played in an advanced wide role under David Moyes.

Under the tutelage of Louis van Gaal, Valencia will have the best of both worlds in his right wing-back role, able to showcase his defensive ability while also making the surging runs United fans have become accustomed to. 

Even with his offensive freedom, it seems he won't be relied on too much to create with Ander Herrera and Juan Mata in the side. As a result, a good amount of his role will be centered around defense.

Van Gaal's confidence in Valencia's ability to play this position is supported by the fact that he reportedly told right-back Rafael da Silva that he is not in his plans, per Colin Harvey of Daily Star.

If those rumors prove to be true, then Valencia has won the battle for right wing-back, and he can begin mending a damaged career by playing in a position that will put all of his attributes on display.