The beauty of the flex position in fantasy football is that it allows managers to get their best players into the starting lineup even when there's a logjam at a particular skill spot. The challenge lies in the fact that choosing between a top running back and a top receiver isn't an apples-to-apples decision.
Looking at Thursday night's game between the Los Angles Rams and the Seattle Seahawks, for example, starting receiver DK Metcalf (5 receptions, 98 yards, 2 TDs) over Darrell Henderson (82 rushing yards, 1 reception, 17 receiving yards, 1 TD) would have been the right call.