'Mini-Messi' Ryan Gauld joins Sporting Lisbon from Dundee United

The 18-year-old, dubbed 'The Scottish Messi', has completed his move to the Portuguese giants and has signed a six-year deal.

Ryan Gauld has joined Sporting Lisbon on a six-year deal (Getty images)

Scottish youngster Ryan Gauld has completed his move to Sporting Lisbon from Dundee United for an undisclosed fee.

The 18-year-old has signed a six-year contract with a buy-out clause of €60 million (£47.8 million), with the fee thought to be in the region of £3 million.

Both clubs confirmed the surprise deal on Tuesday, with Dundee United issuing a short statement: "Everyone at the club wishes Ryan sincere best wishes in his future career."

Having made his professional debut in May 2012 aged 16, the promising youngster's rise to prominence at Tannadice led to an improved deal when he turned 18.

He has drawn comparisons to Barcelona star Lionel Messi due to his small frame and excellent dribbling ability, and a series of eye-catching displays saw him gather serious interest from Manchester United, Arsenal and Liverpool after scoring eight goals in 38 games.

His impressive form led him to being nominated for PFA Scotland Young Player of the Year, and there were widespread calls for Gauld to be called up the national team. Instead, he made his debut for the Under-21 side against Georgia in November 2013.

Former boss Jackie McNamara, speaking to BBC Scotland in December, claimed that Gauld will become a "star" for Scotland.

"He will be one of the greats of our game," the Dundee United manager said.

Gauld will have the opportunity to play in the Champions League next season after Sporting finished second behind city rivals Benfica in the Primeira Liga last term.