Prior to digital, photographing many sports, especially football, was simply too expensive due to the high cost of film and processing. It's fairly easy to rip off 300 to 400 images in a couple hours attempting to capture action. At best, only a dozen images will be satisfactory so you end up filling the recycle bin with unused photos. What a waste of trees and money. The high cost of a digital SLR is easily paid for in less than a year, especially if you shoot 5+ rolls of film per week.
For one of the games I tried a high end 200-400 VR lens on a monopod. Looks great but the 80-400 VR zoom is fraction of the weight and size and allows you to capture images in the 80-200 range. These close-in images would simply be missed with a 200-400. Besides, monopods take a little getting use to. If I need support, I'm much more comfortable with a tripod. With football, the action can start across the field and within a few seconds, can be descending on you at close range. Much too fast to change lenses or cameras. You will lose quality with the 80-400 versus the 200-400 but at least you got the image.
The image above was captured on a D2H with 80-400 VR zoom hand held.