When his loan expired, he returned to Rotherham, and made no further first-team appearances until joining Oldham Athletic on a month's loan in March 2015. Upon joining the club, Sadler was brought by Oldham Athletic as a replacement for Joseph Mills, who suffered a calf–injury. Sadler made his Oldham Athletic debut on 14 March 2015, in a 3–1 loss against Barnsley. Sadler then provided assist for Conor Wilkinson on 21 March 2015, to score the only goal in the game in a 1–0 win over Crewe Alexandra, to end the club's three match losing streak. After making eight appearance for the club, Sadler returned to his parent club on 13 April 2015.