Watford's Nathaniel Chalobah rejected a new contract at Chelsea after concluding he needed to leave to secure first-team football.
The 22-year-old is also targeting a call-up to the England senior team, having been "excited'' by Gareth Southgate's willingness to experiment with younger players.
Like Bournemouth's Nathan Ake and Liverpool's Dominic Solanke, Chalobah finally chose to leave Chelsea earlier this summer in an attempt to progress his career.
His fellow England Under-21 international Ruben Loftus-Cheek has similarly moved on loan to Crystal Palace, with Chelsea having recruited Tiemoue Bakayoko to further strengthen their options in central midfield.