You can tell when Raheem Sterling is at the very top of his game. Just watch the reaction of opposition defenders when he gets the ball.
When he's on it, opponents visibly steel themselves: muscles tighten, shoulders dart back, eyes narrow. Here he comes, get your head on, this could get messy.
At West Ham last Sunday, his every touch provoked panic in a Hammers back line that was twisted, turned and run ragged by the speed, determination and direct action on display from the Chelsea forward.
He would ultimately end up on the losing side at London Stadium, but his man-of-the-match performance drew widescale plaudits.