Born 13/11/91 in Rotterdam, Netherlands.
A player who has developed well ahead of his years, Jeffrey made his first team debut as a 17-year-old during 2009/10, and went on to make another two appearances that season.

Comfortable on the ball and a very good athlete, he had confirmed himself as a key member of the reserve squad prior to stepping up to the first team group under Carlo Ancelotti.

When still a schoolboy, Jeffrey played centre-back in every round in the FA Youth Cup run to the Final and was the top appearance maker in the youth league.

He turned pro in the summer of 2009 and became a Dutch Under 21 international that September 2009 at the age of just 17. His first full international cap came in August 2010 against Ukraine when he was in contest with Andriy Shevchenko. The Netherlands rested their players who had played in the recent World Cup.

Jeffrey signed a new Chelsea contract in September 2010, tying him to the club until 2014. He can play either in the centre or on the right of defence.

In early February 2011 he signed on loan with Championship club Leicester City until the end of the season, linking up with Blues team-mate and compatriot Patrick van Aanholt. Frequently utilised in defensive midfield by manager Sven Goran Eriksson, Jeffrey made 11 Leicester appearances, scoring two thunderbolts against Watford in late April.

He earned his second full international cap as a substitute in June 2011.

At the end of the same month it was annnounced that he would spend the whole of the 2011/12 season on loan at Hamburg with the option of another season in the Bundesliga to follow.