Just as important as fps is shutter response and AF.
There is no problem shooting sports with a 5 fps camera like the Canon 60D, but again the shutter response is a little less than what you want.
The 6 fps Nikon D7000 feels a lot faster in that regard, even though there is only 1 fps nominal difference.
The old Nikon D300 did 6 fps and with good AF and fast shutter there is no problem shooting soccer (which you mentioned).
Of course a 9 fps Nikon D3s is even better. But again, the speed at which it fires the first shot also is a part of the pro feel.
Same story with the 10 fps Canon 1DMK4.
Nice shots BTW...!
I'm not saying one cannot shoot sports at all with a 5fps camera, of course one can on a casual basis. I'm not saying AF, metering, ISO, buffer et al arent important either. They are (and I have, in fact, assumed them as a given in this discussion) but so is the frame rate.
When one is engaged professionally to cover a serious sports event then one has to look for faster cameras. Because then you must not only catch all critical moments but you must catch them in the best possible configuration...that's what you're being paid for. There are, afterall, other sports photographers and the competition is stiff. This is clearly a different world from casual shooting. Under these circumstances a 5-6fps camera simply won't do. An 8fps camera would be generating 33-50% extra shots in bursts of equivalent length and considerably more images to choose from. In soccer the effect is obvious. 9-10 fps would be even better for some frenetic sequences. The (1Dx and D4) would be ideal.
Try covering the first serve of a serious tennis player (like Federer or Nadal). A 6fps camera wont provide enough frames to sequence the serve. An 8fps one provides sufficient critical in-between shots to make a decent stab at it and provides a better chance of catching the exiting ball in the frame. Of course the 12-14 fps of the 1DX would be ideal. 5fps would be a disaster.
You might want to have a look at Marianne Oelund's website [
http://actionphotosbymarianne.com/ ] to get an idea how intense a serious sports pro's work can get. According to her some typical numbers from her sports photography business are:
"At least 8fps burst speed required
About 100 frames taken per minute of action
2000-3000 frames per hour of event
Up to 15 event hours per day."
[
http://forums.dpreview.com/....asp?forum=1021&thread=40819774&page=6]
The D300 with its 6fps was state of the art once upon a time but then so was the Nikon F in 1959. Times have changed and new standards have evolved - both in terms of what can be delivered by photographers and the expectations of clients. I dont think you'll find any serious pro attempting to cover a complete soccer match at 5-6fps in 2012.
The D800 is what it is, an excellent camera for landscapes, studio work and many other things, but heavy duty sports/action isn't its forte.