Sacko completed his move to Elland Road yesterday, 48 hours after linking up with Leeds for their pre-season training camp in Ireland, and United have taken the 22-year-old old with a view to signing him full-time next summer.
The former Bordeaux youngster holds a contract in Lisbon containing a release clause set at 60m euros but clauses of that nature are common at Sporting, used by the club as a means of controlling approaches for their players.
Ryan Gauld, the midfielder who joined Sporting from Dundee United in 2014, is also protected by a 60m euro release clause.
Leeds are optimistic that Sacko would be available for a more realistic fee, around the mark of £1m which Sporting paid when he moved to Portugal from Bordeuax in 2014.
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He is two years into a six-year contract at Sporting’s Estadio Jose Alvalade. Sacko, however, has never featured for Sporting’s first team and has been restricted to appearances for their B squad in Portugal’s second division.
Sporting are open to the option of selling Sacko at the end of his loan at Elland Road and a Leeds statement said: “We are delighted to announce the signing of Sporting Lisbon winger Hadi Sacko on a season-long loan with a view to a permanent deal.”
Sacko has worked with United’s players in Ireland for the past two days and he is set to make his first appearance for the club in their opening pre-season friendly at Shelbourne in Dublin a week today.
The deal to bring him to England takes United’s tally of summer signings under new head coach Garry Monk to three, following on from the arrival of Swedish striker Marcus Antonsson and on-loan Swansea City defender Kyle Bartley.