If you look at the Olympic records you'll find dark-skinned males far, far outperform white-skinned males in running events. Take a look at recent history, Mo Farah, Usain Bolt, Justin Gatley. Then go further back, Colin Jackson, Linford Christie. Look at marathons, the London marathon male event has been won by Kenyans or Ethiopians since 2003. It's not racist to say that the history books state darker-skinned athletes have outperformed lighter-skinned athletes in running. Even football commentators, without mentioning colour but absolutely alluding to it, describe tall, dark-skinned footballers as "athletes" - don't say you haven't heard it a million times. So it's no surprise when people link skin colour to athleticism in terms of running and stamina in football.
With that in mind, you can see why people would link skin colour to athleticism. It may not be true of course, but it's not racist.
That all said, would DCL be classed as black? If so, we've already got a "big black fella who runs all game". lol And he's definitely an athlete, maybe just not a very good goalscorer.