Chelsea's Nathan Ake will spend the season on loan at Premier League new-boys Watford, the English champions confirmed on Friday.

Ake had just signed a new five-year contract with Chelsea, but Blues boss Jose Mourinho believes he needs a lengthy spell on loan before he is ready for action with the Stamford Bridge outfit.

The 20-year-old Dutchman, who can play in either midfield or defence, arrived at Chelsea in July 2011 and lifted the FA Youth Cup in his first season, before winning the club's Young Player of the Year award for 2012-13.

However, Ake has featured just 12 times for Chelsea, including a substitute appearance against Watford in the FA Cup in January.

He spent a month on loan at Reading in March and played five times for the Royals in the Championship.

"Nathan Ake has today signed a new five-year contract with Chelsea," a statement on Chelsea's website read.

"The 20-year-old will continue his development by spending this season on loan in the Premier League at Watford."

Watford have already added 10 new players since last season's promotion from the championship and are reportedly close to signing former West Ham forward Alessandro Diamanti, who has been training with the club.