Liverpool manager Brendan Rodgers said Wednesday the demands of a tough English Premier League season were starting to get on top of teenage sensation Raheem Stirling. The 18-year-old winger has shone since being handed a full league debut by Rodgers in August and he won his first England cap against Sweden in November. However, Sterling has not completed a full 90 minutes since December and Rodgers is convinced that fatigue has played a key factor in checking the progress of the rising star.