Man United close to signing teenage defender Diogo Dalot

The FC Porto defender has played little first team football, but United look likely to trigger the 19-year-old's £17.4m release clause in the coming days.

Manchester United will soon make teenage FC Porto full-back Diogo Dalot their first signing of a big summer for the club.

Manager Jose Mourinho has been keen to get some business done before the World Cup kicks off on June 15th, and Dalot is the surprise name to fill that category.

The 19-year-old has a release clause at Porto of just £17.4m. Though United have not activated it yet, it is widely reported that Mourinho will be greeting him to Old Trafford soon as a Man United player.

Dalot has £17.4m release clause

Dalot will provide competition for ageing first-choice right-back and United captain Antonio Valencia.

He isn't yet ready to be thrown into the first team every week, having played eight times for Porto last season, making his debut in October.

Dalot was mainly in action for the Portuguese club's B team, who are in the country's second tier, last season, only coming in when Alex Telles was injured for a period in winter.

However, he showed his quality then, putting in notably good performances against Sporting in the O Clássico and at Anfield in a 0-0 UEFA Champions League draw against Liverpool.

An attacking full-back, Dalot can play on both sides of defence. Versatility is a trait that Mourinho will never fail to adore. He had been set to replace Ricardo Pereira at right-back for Porto next season, as he's moving to Leicester City, and this deal has reportedly been a surprise to Porto.

Dalot has played 8 first team games for Porto

The club have been trying to get Dalot to renew his contract in order to increase his €20m release clause all season, but have clearly failed. Porto are in financial difficulties in terms of meeting UEFA's Financial Fair Play requirements but will be disappointed to see Dalot leave for so little.

It's a big move, and one that is a risk for both player and club. Young players moving abroad, no matter how talented, can struggle. But t's exactly the kind of signing United need as a club. Not every transfer can be of a ready-made, 'world-class' player like Paul PogbaAlexis Sanchez and Romelu Lukaku.

Thinking of Sir Alex Ferguson's signings, for every Dimitar BerbatovDiego ForlanRoy Keane or Robin van Persie, there was also Cristiano RonaldoRuud van NistelrooyPatrice EvraNemanja VidicPeter Schmeichel.

Rated very highly in Portugal, where he plays for the country's under-21 team, Dalot will likely be back-up to Valencia next season, seeing the more senior Ecuadorian slowly decrease his playing time.

19-year-old to be back-up to Valencia

It's the first sign of Mourinho looking to improve his defence, which he believes will allow him to compete for the Premier League title with Manchester City.

Italian full-back Matteo Darmian looks set to join Juventus, and Daley Blind's time at the club is up. Tottenham Hotspur's Toby Alderweireld is reportedly another of Mourinho's targets, while Brazilian midfielder Fred has been heavily linked in recent weeks.