Manchester United has locked up Rafael da Silva. The 21-year-old right back signed a four-year extension with the Red Devils that will keep him with the team through 2015-16 season, according to the team's official site.

Longtime manager Sir Alex Ferguson was pleased United could lock up the rising star, who has impressed his boss in limited playing time since joining the team.

"Rafael is one of the club’s brightest young prospects; he has no fear of playing and has great belief in himself.

"The boy has developed immensely since joining United, his energy and enthusiasm are a joy to watch. Rafael has all the attributes to become one of the best full-backs in the world and I am delighted he has signed a new contract."

Rafael has played 90 games since joining Manchester United four years ago. He features terrific pace, which allows him to get forward to help the attack, and has started to develop into a much more sound defender as well.

His new deal fits the mold of Ferguson's plan over the past few seasons. The team has gotten away from relying on high-priced transfers and have instead started to target younger talent or re-signed their own youthful players to continue their development.

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Not only does it allow the squad's young players to grow together, which should improve chemistry when they are asked to take on a more important role, but also limits the financial risks the Red Devils are forced to take.

Although Rafael has a boatload of talent and could have probably received more guaranteed playing time elsewhere, he has always seemed comfortable at Old Trafford. By the time his new contract ends, he should be a big part of the United back line.

Getting him locked up gives the Red Devils more flexibility at the back as they look to return to the top of the Premier League after finishing second last season. After making an impact near the end of last season, a breakout campaign is a distinct possibility.

Re-signing players is often just as important, if not more so, than the transfers a team brings in. That's certainly the case here as United secures a very promising young player.