Sam Walker joined Chelsea from Millwall's youth team in 2007 for a fee of around £175,000. He is described as a "good shot stopper who collects crosses and distibutes well".

Sam joined Norwich on loan in March 2009 playing for the Under-19s in their 1-0 defeat at Reading on 21st March 2009 after Jed Steer was called up by England and Declan Rudd and Sam Grieverson both sidelined through injury

Walker was part of the Chelsea youth team that won the 2010 FA Youth Cup defeating Aston Villa in the final

On 24th March 2011, Sam joined Barnet on loan until the end of the season, becoming new manager Martin Allen's first signing. He made 7 appearances for Barnet

In July 2011, he joined Northampton on a season long loan but returned to Chelsea on 23rd December 2011, after making 21 league appearances, when the new Cobblers boss Aidy Boothroyd signed Shane Higgs as first choice keeper.

Walker joined Yeovil on loan on 19th January 2012.