The Leeds United winger struggled for game-time at Elland Road in the previous campaign.
The Gunners legend has left his role as a coach with the Arsenal Under 18s.
Newcastle United's Dwight Gayle has been training with the club, after completing a move from Crystal Palace.
Norwich City have reportedly failed with a £7m bid for Britt Assombalonga.
Thomas Vermaelen is reportedly on West Ham United manager Slaven Bilic's wishlist.
Glasgow Rangers signed Michael O’Halloran in the January transfer window.
The midfielder played under Powell at Huddersfield and the pair are set to work together again at Derby.
Jack Grealish is expected to play a key role for Aston Villa next season.
Diego Poyet says that he wants to remain at West Ham United next season.
The defender played for both Spurs and Liverpool in his 17-year professional career.