Matrix: 3D color matrix metering II for sports?

How would the nikon d5100 with the Matrix: 3D color matrix metering II do in focus tracking?

No no no no… Metering determines the correct exposure for you photos (you choose the ISO). Metering has nothing to do with AF.

With a good lens, the 5100 is OK for sports.

YOU also have to be able to keep up with the action.

Metering is a separate thing. It measures the amount of light that passes through the lens. It has nothing to do with focusing.

The D5100 is equipped with the 11-point Multi-CAM 1000 sensor module, additionally the centre point is a cross-type sensor. It does do 3D-tracking, and is the same AF-sensor fitted to the D200, D90 and D5000. The problem is that this system isn't the smartest system, and is a little sparse on points.

Compare this to a similarly priced second hand camera such as a 1D mark II, or 1D mark IIn or Nikon D300 (yes, up until recently Canon has consistently beaten Nikon on AF), you'll see a huge difference. The 1D mark II cameras all came equipped with a 45-point TTL-AREA-SIR autofocus system, with seven cross type sensor, this system can activate up to thirteen surrounding points to give extra accuracy in AI-servo focus mode, additionally this system can be told to ignore certain things such as stationary objects moving in front of the moving subject which may confuse the system. The D300 is armed with a 51-point Multi-CAM 3500 module. So you can see that there's still a huge gulf of difference from an older professional camera which has much more advanced focus tracking algorithms.