Barcelona winger Gerard Deulofeu has joined Watford in a deal which could rise to 17 million euros.Barca are also due to receive a percentage of any sale should Deulofeu leave the Premier League side in the future.“FC Barcelona and Watford FC have reached an agreement for the transfer of Gerard Deulofeu to the English club,” the Catalan club said in a statement on Monday.“We have agreed on a fee of 13 million euros, plus 4 million in variables. FC Barcelona will also receive a percentage of any future transfer operations to other clubs.”Deulofeu joined Barca as a nine-year-old and came through the club’s academy, making his first-team debut in 2011.