Defensive midfielder Isaac established himself as a senior member of the under-21 side in the 2013/14 campaign, captaining the team on a number of occasions.
The England youth international is comfortable on the ball, strong in the challenge and leads by example with his commitment and tenacity.
Isaac made his debut for the first team in the Capital One Cup victory at West Bromwich Albion in September 2013, partnering Per Mertesacker in central defence. He made 15 appearances for the second string last season and three in the under-19s' Youth League campaign.
The Essex-born youngster signed a new contract with the club in February 2014 and was named in the first team's Champions League squad last season.