He has previously played for Morris County Colonials, Kaya FC, and the Philippines national football team.

Greatwich began his career at Brighton and Hove Albion when he was recommended to the club by his PE Teacher aged 12.

Following his release from the club in 2003, Greatwich pursued a soccer scholarship in the United States, playing for Drury University and Hartwick College.

Upon graduation, Greatwich returned to UK and following an unsuccessful trial with Kilmarnock in the Scottish Premier League, he joined non-league clubs Lewes FC & Bognor Regis Town.

Later that year, Greatwich played in the 2008 AFF Suzuki Cup qualifiers in Cambodia where the side again would be eliminated from the tournament this time on the basis of goals scored.

In their first group game against Singapore, Greatwich scored an injury time equaliser to produce one of the biggest shocks in AFF Suzuki Cup history.

In March 2015 Greatwich announced that he was taking a break from the national team, specifically to spend more time with his family and his newborn son.

Greatwich had previously served as the club's head coach in an interim capacity in numerous occasions such as in the 2015 UFL Cup knockout stage.

Following Dooley's departure, Greatwich remained as Assistant Coach under former England manager Sven-Göran Eriksson for the Suzuki Cup, where they led the team to the semi-finals, losing to eventual champion Vietnam.