In the 2007–08 season saw Sadler suffered a knock and Achilles problem to the start of the season. After missing out the first two matches, Sadler made his first appearance of 2007–08 when he came on as a substitute for Fabrice Muamba in the 80th minutes, in a 1–0 loss against West Ham United on 18 August 2007. Sadler then provided assist for Garry O'Connor in the 27th minutes, in the first round of League Cup, in a 2–1 win over Hereford United on 28 August 2007. However, Sadler struggled for the first team place after losing his left-back position to Franck Queudrue and Liam Ridgewell. As a result, Sadler was sent to play in the reserve. But in December, Sadler returned to the first team in the left-back position in his first league appearance since December, in a 2–1 loss against Newcastle United on 8 December 2007. However, on his next appearance against Reading, Sadler came under criticism when his back-pass short led to goalkeeper Maik Taylor brought down Stephen Hunt in the penalty box, leading Hunt to take the penalty himself and converted the penalty successfully. After the match, Taylor defended Sadler, stating he could one day bounce back.