Ryan Sessegnon is set to stay with Fulham next season after signing his first professional contract, amid links to some top clubs.
Middlesbrough forward Viktor Fischer has joined Mainz, the Bundesliga club have announced.
Reports in the Italian media suggested he will complete a £5.3 million permanent transfer.
Parker, 36, helped his last club Fulham, for whom he played for four years, to reach the Championship playoffs.
Klinsmann, 52, has been out of coaching since November, when he was sacked by the U.S.
Hughes, 22, has put pen to paper on a five-year contract at Vicarage Road and joins for an undisclosed fee.