He was most recently the head coach of EFL Championship club Plymouth Argyle Foster began his career at the Liverpool FC Academy working under the tutelage of Steve Heighway and Sammy Lee.

He remained in post for the 2011 season and again secured Premier Division status for the club whilst also guiding Dundalk to the All Ireland (Setanta) Cup final.

As part of the 2011 English FA cohort, he graduated alongside alumni including Ole Gunnar Solskjær and Gianfranco Zola Citing family circumstances, Foster returned to England to resume his coaching career.

Upon the departure of manager Mark Robins to Huddersfield Town in February 2013, Foster was appointed First Team Coach, initially working alongside Lee Carsley and subsequently Steven Pressley.

During his tenure at the club he oversaw the development of a number of players who went on to earn full international honours, including James Maddison, Callum Wilson, John Fleck and Cyrus Christie.

England U19s went on to win to 2022 edition of the U19 European Championships, beating Israel (3–1 AET) in the final at the Anton Malatinský Stadium in Trnava, Slovakia.

During his time within the England Men's coaching set-up, Foster has played a role in the development of a number of players who have achieved full international status, including Phil Foden, Bukayo Saka, Jadon Sancho, Callum Hudson-Odoi, Mason Greenwood, Conor Gallagher, Emile Smith Rowe and Yunus Musah.