Manchester United boss Jose Mourinho is reportedly fearful that £75million striker Romelu Lukaku has lost some of his speed because he's added too much muscle to his frame.
The Sun claim that the Belgian striker, who joined Old Trafford in the summer, has gained around half a stone since his big-money switch.
Club doctors insist the weight is all muscle rather than body fat and there are no lifestyle concerns around Lukaku.
However there is a concern that the 24-year-old has lost a yard of pace recently because of his bulked-up frame.