Manchester United are said to be close to completing the signing of Porto right-back Diogo Dalot as Jose Mourinho looks to strengthen his back line ahead of next season.

The 19-year-old defender made his debut for the Portuguese club last season and immediately impressed during his seven first-team appearances in all competitions.

According to BBC Sport, Dalot has a £17.4m ($23m) release clause in his contract with Porto, and any interested club will have to match that to convince the latter to part with the young defender. The report claimed United are yet to meet the release clause but have held talks with regards to a move.

The talks between the English Premier League club and their Portuguese counterparts are reported to be at an advanced stage with a deal said to be imminent in the coming days. Dalot has represented Portugal at Under-21 level and made his first-team debut for his club in February this year.

Mourinho is said to be keen to bring the teenage defender to challenge Antonio Valencia, who is currently first-choice at right-back. The Ecuadorian has been a regular since joining the Red Devils in 2009, but at 33 years old, he is certainly in the latter part of his career.

Diogo Dalot
Diogo Dalot is close to joining Manchester United. In this picture, FC Porto's defender Diogo Dalot from Portugal attends FC Porto Gala Dragoes de Ouro 2016 - 2017 at Dragao Caixa in Porto, Portugal, Oct. 25, 2017. Carlos Rodrigues/Getty Images

Matteo Darmian was brought in a backup for Valencia, but the Italian failed to settle in the Premier League and is now expected to leave in the summer and join Juventus in his homeland. Dalot is unlikely to be a starter, with Valencia being one of the manager’s favorites, but is certain to get game time with United competing in four different competitions.

Dalot is primarily a right-back but can also play at left-back, another problem area for Mourinho. Luke Shaw, the current incumbent, has not convinced Mourinho about his potential, while Daley Blind, who has been used there, is likely to leave the club this summer.

Ashley Young, primarily a winger, was used at left-back on numerous occasions last season, but the United boss is said to want a more traditional defender on the left side of his back four. According to the Mirror, the Old Trafford club are said to be interested in Barcelona full back Jordi Alba.

The Spain international has two years left on his deal with the Catalan club and talks over a new deal seem to have stalled. Alba had a stellar season for Barcelona as they won the domestic double, but is yet to be given an improved deal.

The player’s agent has criticized the club after they failed to live up to their promise of handing the defender a new contract. If he refuses to sign a new deal, United and Chelsea, who are also interested, could make a move in the coming weeks.

“[When] Raul Sanllehi [now at Arsenal] was still at the club when they told us not to worry, that they were going to call us to renew,” Alba’s agent Vicente Fores said, as quoted by the Mirror. "But we are still waiting. It’s been a year and a half now,” he added. “We don’t understand anything, maybe it’s normal for Barca or maybe they’re not happy with the performances of a player included in FIFA’s XI and who is the defender with the most assists in European football."