In this particular case, focusing on the front rider would result in a more pleasing picture than having more DOF. It would put the back rider slightly out of focus, but still very recognizable. . .
I agree with the idea, Slobodan, and you're right that the major figure should be the one in focus, but Chris was shooting with a 24-70mm f/2.8 zoomed to 32mm at f/2.8. ISO 2000. For starters, that lens has no optical stabilization, so it's not the greatest choice for this kind of work. He was focused on a spot 5 meters away -- about 16 feet. I'd guess that was roughly the distance of the more distant rider. If that's the case, the closer rider would be about 6 feet out. If he focused on the closer rider, at 32mm and f/2.8 he'd have a depth of field range of roughly 5'9" to 6'3". The distant rider would be very
out of focus.
As for "stopping the action," I do not think it is quite necessary either. Slight (or even not so slight) motion blur can add a sense of dynamics to the picture. The best motion blur would be, of course, a result of panning.
In conclusion, you do not always need more DOF, higher ISO, or higher shutter speed for images like this. Just a good eye and good reflexes
Right on. Motion in this kind of picture adds the kind of dynamism you want. But to get what he's after I think Chris is going to have to crank his D7000 on up to ISO 6400, and, possibly, stop down a bit because he's going to need a bit more DOF. If I were Chris I'd switch to a 24-120 f/4.0, which has optical stabilization, so the motion is in the subject, not the camera. There's going to be some noise at ISO 6400, but for this kind of picture that shouldn't matter much. It isn't landscape. If the noise gets too high you always can convert to B&W, which, in my own estimation is better for this kind of picture than color. Another useful trick is to pre-focus so focus doesn't jump around when you're shooting. That requires that you set up your Nikon so you're using AF-ON exclusively for focusing, which is what every pro I've ever talked to does. Once you set up your camera that way you'll never go back to a half-press of the shutter button.